COSTA MESA, Calif. -- Jahleel Addae grew tired of writing checks to the NFL. The hard-hitting safety for the Los Angeles Chargers had accumulated nearly $50,000 in fines over five seasons for dangerous hits to the neck and head area of receivers.

Those hits also caused him to miss time because of injuries. So what's Addae's solution? Aim low.

That's the mindset of defensive players in the league with rules established for hits near the neck and head area on defenseless players resulting in personal foul penalties, hefty fines and suspensions that could cost their teams wins in the long run.

"Early in my career I was going high," Addae said. "And I learned from my fines and a lot of plays I did that wasn't necessary, and I've lowered my target."

Addae is having one of his best seasons as a pro, with 57 tackles and five pass breakups through eight games.

With the rules established to protect defenseless players and prevent hits to the head, defensive players have to figure out a new target area, coined the NFL strike zone.

"Early in my career I was going high. And I learned from my fines and a lot of plays I did that wasn't necessary, and I've lowered my target." Chargers safety Jahleel Addae on his tackling technique

However, some receivers have griped about defensive players hitting them low, which in turn could cause season-ending leg injuries.

Players on offense receive protection under the NFL's defenseless player rule if, among other things, they are attempting to make a catch but have not yet had a chance to become a runner.

According to new league rules, for a passer in the pocket the NFL's legal strike zone is below the neck and above the knee. The legal strike zone for a receiver attempting to catch a pass is below the neck.

So that protection prevents defensive players only from delivering a hit to the head or neck area, or with the crown of the helmet. But receivers can still be hit low.

NFL spokesperson Joe Lockhart said the league has had 47 health and safety rule changes since 2002.

According to Detroit Lions defensive back Glover Quin, Arizona Cardinals receiver Larry Fitzgerald said he would pay defensive players' fines if they hit him high and received a penalty.

"He's big on don't hit him low, hit him high," Quin said. "He'll tell you on the field, like, 'Hey, bro, I'll pay your fine for you. Like, don't hit me in the legs.' He'll rather you hit him up high. Don't take his legs, because obviously you need your legs to run."

According to ESPN's Kevin Seifert, NFL injury data has shown no dramatic uptick in knee injuries as a result of the new rules.

The rules not only affect players, but the officials who have to govern the rules as the plays happen.

Jim Daopoulos worked as an NFL official for 11 years and served as the league's supervisor of officials for 12 years. Now he works as a NFL rules analyst for ESPN.

With the prevalence of CTE studies in the mid-2000s, Daopoulos said, the league began an effort to limit hits to the head, which has evolved into the NFL strike zone for defensive players we see in the game today.

"The primary focus from Day 1 was the protection of the players," Daopoulos said. "It started off being the quarterback, and then it turned into being the defenseless player, where we ended up getting about eight different positions where players are basically defenseless -- they couldn't see something coming and they weren't able to protect themselves. And you try to give them as much protection as you could.

"But it's so difficult for defensive players because their thought process is, 'Get that guy to the ground.'"

However, gripes from receivers have put defensive players in a bind -- hit a ball carrier high and get fined or suspended; hit him low and suffer from verbal abuse or fights from offensive players. The dilemma has defensive players searching for that sweet spot in the NFL strike zone.

"Back when I played, everything was sort of legal," said Philadelphia Eagles coach Doug Pederson, who played 12 years in the NFL as a quarterback. "Every contact, every hit, was legal, and slowly but surely, they took the head and neck area away. And that's the thing with the game today.

"It's about player safety. I think you have to continue to talk to your receivers on how to protect themselves from hits that are low. It's a part of the game, and it's going to happen. Defenders are lowering their target zones and doing what they're coached to do and playing by the rules."

Chargers defensive coordinator Gus Bradley said he teaches his defensive players to aim for an area between the mid-thigh and below the shoulder. However, the problem for defensive players is they are hitting a moving target, and the strike zone can change in a split second once the ball carrier moves.

Add in the fact that defensive backs are the last line of defense and don't want to give up explosive plays, and defenders are trying to get ball carriers down by any means necessary.

"It's one of those things where the strike zone is affecting these guys some because of where they want to target and how they want to hit it," Bradley said. "I don't think it's malicious. It's not going after the knee and trying to take his knee out, but you've got to be aware of it.

"We teach our guys even on a blitz that if you come through a gap and you're free, where is your strike zone on a quarterback? And there's only a certain area. It's like a strike zone -- above the knees and lower than the shoulders. And if the quarterback ducks his head, how do you adjust to it? So there's far more teaching going into that aspect than ever."

Here are five examples of questionable hits this season that raised eyebrows among NFL ball carriers:

The situation: Dolphins at Chargers, Week 2

The Chargers trailed 10-3 in a Week 2 contest at home against the Miami Dolphins. On second-and-4 from midfield with 16 seconds left in the first half, Jay Cutler found DeVante Parker on an out route for what would have been a first down, putting the Dolphins in field goal range. The Dolphins punted two plays later and didn't get any points as a result of Addae's play. However, Addae took Parker's legs out and he landed out of bounds, unable to get his feet down for the catch. Addae and Parker had words on the field, and a minor scuffle ensued in the tunnel as the two headed to the locker room for halftime. Parker did not suffer an injury and continued to play the rest of the game.

Here's NFL.com video of the play.

"It was a two-minute drill," Addae said. "If I hit him up top and he gets his feet in bounds, they kick a field goal. My thought process is he's trying to catch the ball, I'm going to chop his legs from under him to force him out of bounds and take them back to the 50-yard line and keep them out of field goal range.

"I'm going to do my job every time, because if a receiver comes downhill and crack back on us and decleats us, it's a good play by them and they get a plus on their grade sheets."

The situation: Redskins at Rams, Week 2

In a Week 2 contest against the Los Angeles Rams, Washington Redskins receiver Terrelle Pryor Sr. caught a shallow crossing route across the middle of the field with seven minutes left. Rams safety Cody Davis raced up from the secondary and hit the 6-foot-4 Pryor around his right knee. Pryor did not suffer an injury on the play, but later took to Twitter, asking Davis to please hit him higher in the future.

"I just had a message I wanted to send," Pryor said about the play. "Some people said, 'It's football, Don't cry.' But, I mean, that's how I felt. Usually I don't do that. I don't whine about things that happen. I don't whine about bad things that happen with me.

"That's just what I firmly believe. It doesn't matter how big I am. It doesn't matter how much smaller the guy is for me. I just feel like before the ball even got to my hands, the dude's chopping my legs out."

The situation: Giants at Browns, preseason

In a preseason contest against the Cleveland Browns, Odell Beckham Jr. caught an out route in the second quarter and was cut down by Briean Boddy-Calhoun. Beckham winced in pain after the play and flung the ball in the direction of the Browns' defense in frustration. He suffered a sprained left ankle on the play that forced him to miss the rest of preseason and the opening game of the regular season. He suffered a fractured ankle in a Week 5 contest against the Chargers on the same leg. It required surgery, ending his season.

Here's the play. Beckham took the high road afterward.

"I don't know, it's just football l guess, preseason," he said. "I'm not really the judge. It's just football in my opinion."

The situation: Ravens at Vikings, Week 7

In the opening quarter, the Baltimore Ravens had second-and-10 from their own 35-yard line when Joe Flacco connected with Mike Wallace on a slant route. Vikings safety Andrew Sendejo delivered a blow to Wallace's head with his shoulder that knocked off the receiver's helmet and jarred the ball loose. The hit sent Wallace into the league's concussion protocol after the game. Sendejo received a flag for unnecessary roughness on the play and was suspended a game for violating player safety rules. Sendejo's hit is an example of the blows to the head the NFL is trying to avoid.

"I think the receiver took five steps after he caught the ball and I think [Sendejo] hit him with a glancing blow," Vikings coach Mike Zimmer said in defense of his player. "He established position as a runner, took two extra steps. Xavier was trying to pull the ball out, which he ended up doing. The guy went down a little bit, but in my opinion, [Wallace] was a runner."

The situation: Dolphins at Ravens, Week 8

On third-and-10 from the Dolphins' 20-yard line early in the second quarter with the Ravens leading 13-0, quarterback Joe Flacco was flushed out of the pocket and scrambled down the right sideline for 9 yards. Flacco slid feet first at the end of the play to try and protect himself, but as he got down Dolphins linebacker Kiko Alonso hit the veteran signal-caller in the head, knocking his helmet off and igniting a melee on the field. The hit forced Flacco to leave the game.

Alonso was flagged for unnecessary roughness on the play. He also was fined $9,115 for the late hit but did not receive a suspension from the league. The dangerous play is another example of hits to the head the NFL is attempting to avoid by lowering the target of a defensive player.

Here's the play.

"It was bang-bang," Alonso said. "He got to the point where I thought maybe if he slid a second sooner, I would've anticipated him sliding and not hit him. But I think he was a second late."

ESPN NFL Nation reporters John Keim, Michael Rothstein, Jordan Raanan, Courtney Cronin and James Walker contributed to this report.