SANTA CLARA, Calif. -- While serving the final day of his two-game suspension from the NFL, San Francisco 49ers linebacker Reuben Foster spent this past Sunday like many fans at home: living and dying with every snap.

Before the Niners and the Detroit Lions kicked off, Foster went in search of food -- quickly coming to the realization that Chik-fil-A is, indeed, closed on Sundays -- before realizing he was running late for the start of the game. Foster hustled home without a meal and proceeded to spend the rest of the afternoon yelling at his television and cheering on his teammates.

When Foster woke up Monday morning, his suspension was officially over and the second act of his young football career was ready to begin.

"It was like a holiday," Foster said. "Just knowing I can come back and play the game I love for real. I'm just happy. … [I'm] playing my cards right, doing good off the field and on the field. [I] just don't do nothing off the field, so I won't be off the field again."

What has been a long and tumultuous offseason for Foster is now officially in his rearview mirror as he has spent all week preparing for Sunday's game against the Kansas City Chiefs. It will be the first game of Foster's second NFL season.

It might also be the first game in a long-term partnership with fellow inside linebacker Fred Warner. It's a partnership the 49ers have been eyeing since April's NFL draft.

At time of the draft, Foster's future with the team remained in doubt as he dealt with allegations of domestic violence and an arrest for possession of marijuana. The domestic violence charges were dropped after his former girlfriend said she lied to police and Foster completed a course to avoid further punishment for the marijuana charge. But those issues resulted in a two-game suspension from the NFL for violation of the league's policies on substance abuse and personal conduct.

It left the 49ers in a precarious position at the time of the draft. They had already grown fond of Warner from what they'd seen of him at BYU and liked him even more when they had a chance to sit down with him and see his knowledge of the game first hand.

When the Niners selected Warner with the No. 70 overall pick, they instantly had some insurance as Foster's legal situation played out. But in a more ideal scenario, they had a potential long-term running mate to line up next to him.

Now that Foster's two-game suspension is over, that pairing could make its debut as soon as Sunday against the Chiefs, though coach Kyle Shanahan has maintained the Niners are still sifting through their options with Foster returning and Malcolm Smith back from a hamstring injury.

Whether it's this week or some point in the future, it's not hard to envision Warner and Foster as the young, athletic inside linebackers set to follow in the franchise's lineage of top-level linebacker play.

"They have a ton [of upside]," cornerback Richard Sherman said. "They're both instinctual, they trust what they see, and that's a big part of this game is just being able to play fast and seeing something and being able to react to what you see. There's a lot of guys who can be smart on paper and then see it on film and say, 'Man, this is the answer and this is the answer.' But going out there and translating it to the field is difficult for a lot of guys, and those guys do it as well as anybody."

While Foster's suspension and Smith's injury obviously didn't help the Niners in the first two weeks, it might also serve them well for the long haul. It allowed Warner the opportunity to dive head first into the deep end of the NFL pool.

Coming out of BYU, Warner was known for his intellect and athleticism, playing all over the Cougars' defense and often handling a sort of linebacker-safety hybrid role. The question about Warner was whether he was physical enough to play linebacker in the NFL. He quickly answered that in training camp and then promptly put up 12 tackles and a forced fumble against Minnesota in Week 1. He followed with 10 more stops last week and his 22 tackles through the first two weeks rank third in the NFL.

Despite a quick start, Warner has been even quicker to point out his mistakes. He counts issues with his drops and breaks in pass coverage as a couple of weaknesses to clean up. Those types of small details have become the focus of his seemingly non-stop film sessions.

In Foster and Smith's absence, Warner has played middle linebacker and been entrusted to handle all the defensive calls via the helmet head set. It's a big responsibility for anyone, but especially a rookie who is playing the position for the first time.

"He's a film junkie," defensive coordinator Robert Saleh said. "You see him eating breakfast and watching tape. He's sitting at a table by himself in the cafeteria and he's got the tape rolling. He's always deep in the film. If he continues to progress the way he is, he does have a bright future."

Saleh also has preached the importance of consistency, something Warner hasn't been able to show yet simply because he hasn't had the opportunities to build his résumé yet.

"I should be putting in the most time out of any position because I have got to make sure everybody is in position to make plays," Warner said.

Getting Foster back gives the 49ers plenty of options as they move forward and though no decision has been made on how the Niners will line up this weekend, it seems a safe bet Foster will return to his weak side linebacker spot.

"Reuben's one of our best players," Shanahan said. "I think he plays the position very well."

If Warner can continue doing the same at his spot, the Niners could soon have two linebackers to fit that description.