SANTA CLARA, Calif. -- It's a Thursday night just two weeks before the start of San Francisco 49ers training camp, and karaoke night at Khartoum Lounge in Campbell, California, has just taken an enormous and outlandish turn. Standing on stage are roughly 13 feet and 610 pounds of ballad-belting bookend offensive tackles.

Joe Staley and Mike McGlinchey generally prefer to compete at karaoke, flying solo on stage aside from the occasional dual foray into the Backstreet Boys.

Love it 😂 Unfortunately auditions are closed fellas! @jstaley74 @mmcglinch68 https://t.co/hnAfv0a1QB

— Backstreet Boys (@backstreetboys) August 30, 2018

Instead, they have something new and -- given the notes required to nail the performance -- risky in mind.

The song choice is "Shallow," the Bradley Cooper/Lady Gaga duet (the tackles repeatedly pronounce her name "Guh-gah") made famous by the 2018 movie "A Star is Born." Staley steps into the role of Cooper, dropping his voice to set the stage for McGlinchey.

"I set him up with a real low Bradley Cooper bar and then I stopped singing and I went, 'All right, blow them away,'" Staley says.

McGlinchey, whose go-to song is "Mr. Brightside" by The Killers, says he's rehearsed the song many times on his own, but it's different on stage when people notice, camera phones come out and it's time to put on a show. McGlinchey digs deep, attempting to take his voice to places it normally doesn't go.

On this night, it's just not happening.

"I just couldn't hit the high notes," McGlinchey says with genuine disappointment in his voice. "I was so upset with myself after that. I failed so hard at Lady Gaga. I thought I could do it. I just couldn't."

Although "Shallow" might have been a miss, the depths of Staley and McGlinchey's friendship go well beyond their musical stylings.

While wide receivers and defensive backs have earned a reputation for their big personalities (and egos), anyone who has spent time around a locker room knows it's often the offensive line that most effectively represents the heartbeat of a team. In San Francisco, the case can be made that Staley and McGlinchey best set the tone.

“They have a very unique relationship," quarterback Jimmy Garoppolo said. "The age difference is so different, but they’re so similar in their personality. It’s fun to be around those guys. They always keep it light. And when you get out there between the lines they’re different people in the huddle and I love that. You’ve got to have guys like that who can know when to turn it on and know when to turn it off.”

Bickering like brothers, laughing like friends

Sitting next to each other for an interview in the 49ers' public relations office, Staley and McGlinchey are 90 minutes removed from a training camp practice (Staley is fresh after a veterans' rest day) and have quickly shifted gears into what might as well be a stand-up comedy act.

Over the course of about 33 minutes, McGlinchey and Staley bicker like brothers and laugh like best friends while discussing everything from Staley's license to curse in front of McGlinchey's mother -- Staley is a dad and McGlinchey is not, she reasons -- to their favorite karaoke tunes to how their fast and easy relationship has become integral in each other's careers and to the 49ers' building.

Long before Staley was even aware of McGlinchey, the second-year tackle had been keeping tabs on -- and looking up to -- the 12-year veteran. When McGlinchey was early in the college recruiting process, the Notre Dame strength coach was Paul Longo, who held the same position at Central Michigan when Staley was there.

Longo, who was part of the ND group recruiting McGlinchey to the Irish, told McGlinchey that he reminded him of Staley and, as McGlinchey began to realize that his path in football would be at offensive tackle, he decided it was time to study up. At the time, the Niners were one of the NFC's best teams and Staley was one of the key components of their run to Super Bowl XLVII, making him a natural starting point.

McGlinchey was blown away by Staley's combination of athleticism and technique and though the 49ers lost that game to the Baltimore Ravens, McGlinchey watched it on repeat and changed his high school number to Staley's 74.

"I knew everything about him before I got here and I've probably watched that Super Bowl on film, like 40 or 50 times," McGlinchey says. "I thought it was one of the best games I've ever seen a left tackle play."

(At this point, Staley stops McGlinchey. "You’ve never, ever complimented me like that," Staley says. "That was really nice.")

Staley, meanwhile, knew nothing of McGlinchey until the Niners used the No. 9 overall pick on him in the 2018 NFL draft. After sending a congratulatory text to McGlinchey, Staley quickly went searching for anything he could find on his new teammate and discovered videos of McGlinchey interviews from his time in South Bend.

The first thing Staley noticed was just how polished McGlinchey was in front of reporters, something McGlinchey attributes to getting weekly practice at Notre Dame and something Staley didn't get as much of at Central Michigan, a place McGlinchey likes to call "The Little Sisters of the Poor" as a jab at Staley.

"I never experienced the big shining lights like Mike did," Staley says. "That was my very first impression was like this kid is a politician. So, I was going to try to break him down and get to the real Mike. I was really shocked. Because I thought his personality was very square like, 'Hi, how are you, Mike McGlinchey here, let me tell you why I'm the best.' And really he's like, just 'Philly Mike.'"

Staley, who is 10 years McGlinchey's senior, says he never felt threatened by McGlinchey's arrival and related to coming in as a first-round pick with big expectations. Within a week, the two went to a nearby sports bar for burgers and beers, realized how much they had in common as self-described "loud, obnoxious people" and, not long after, how much they could help each other.

The ways that manifested in their first season together were quite different. For McGlinchey, it was important to have a veteran sounding board who could offer tips on pass-rushers and technique and, perhaps most importantly, lift him up when inevitable rookie struggles hit.

In a game late last season McGlinchey was struggling. As the game was going on, Staley noticed and reminded his rookie teammate that the guys on the other side get paid to play, too.

"There's a lot of people in the position that he's in that would have viewed it kind of as a threat almost," McGlinchey said. "Luckily, Joe is a good enough guy and good enough teammate and comfortable enough in his own skin that he was pretty selfless. He was there for me 100 percent."

Balancing fun with success

For Staley, who has seen and done almost everything during his NFL career, McGlinchey's youthful exuberance has helped revitalize him. After a dreadful 2-14 season in 2016, Staley strongly considered retirement. Head coach Kyle Shanahan's arrival had given him some renewed vigor, but McGlinchey's arrival the following year has pushed that to another level. Staley even signed a two-year extension in June that takes him through the 2021 season and should allow him to retire with the only NFL team he's ever known.

Staley said he and McGlinchey are constantly bouncing ideas off each other and watch each other's reps in order to offer technique tips in real time.

"When he got drafted, I was getting to that point that I was going through a rough patch from Year 9 to 11 of like, do I want to keep playing football?" Staley said. "How long do I want to do this? And just having that kind of little brother-big brother relationship that he brought in and got along so well kind of really reinvigorated me a little bit."

While laughter might be a focal point of their friendship, it doesn't come without conflict. Some of it is good-natured -- such as the seven minutes and 11 seconds of arguing about what Staley calls McGlinchey's politician personality or the five-minute debate about whether McGlinchey didn't work out and hang out with Staley as much as promised in San Diego in the offseason -- but it can also turn serious, especially when those disagreements take place on the field.

In fact, just a couple of hours earlier, Staley and McGlinchey got into it over something on the practice field. They wouldn't disclose the specifics of what they disagreed on but both acknowledged that they were genuinely angry at each other.

"They are both smart guys who really study their craft, who study each other," Shanahan said. "They both compete more than anything even though they are, I joke BFFs, but they still are going to hate on each other too and try to get after each other because they definitely are competitive. I think that's something a veteran like Joe needs at this time in his career and I think it's great for a younger guy like McGlinchey to have a reminder on the other side that he doesn't have all the answers, that there's a lot more he can learn and he can get a lot better also."

Of course, that anger usually gets swept away in about an hour without apologies. After all, when practice and meetings are finished, it's time once again to bring a little levity to the locker room or head out for more burgers and beers, a round of karaoke, a sporting event (San Jose Sharks hockey games are a favorite) or a stop at Staley's house to hang out with his daughters, Grace and Audrey.

Niners players and Sharks Alumni going wild after the W 🔥🔥🔥🔥 pic.twitter.com/bNS9lMk11V

— Sharks on NBCS (@NBCSSharks) April 24, 2019

"I could not do another job, honestly," Staley said. "My personality would be really hard to work in a normal job."

On that, McGlinchey and Staley will always agree.

"I'd really struggle outside of the football realm," McGlinchey said. "But I think I think we just know what's important to us. It's like, we love to have fun. But we both want to be very good at what we do. And when it's time to play football and watch film and all that, it's serious. And when it's living life and being around your teammates, it's about having fun and enjoying the time that we spend together."