One thing they share is football, with Leinart the quarterback for No. 1 Southern California and Jarrett his favorite target.
Otherwise, they wouldn't seem to have much in common, since Leinart is a 22-year-old fifth-year senior from nearby Orange County and Jarrett is a 19-year-old sophomore from New Brunswick, N.J.
Appearances can be deceiving.
Both needed a roommate last summer, so in their words, they hooked up.
It has worked out well.
"We're kind of down to earth, laid-back," said Leinart, the Heisman Trophy winner. "We really get along. We play a lot of video games."
Said Jarrett: "Me and Matt have always been cool ever since I first got here. We have the same personality - we don't let our heads get too big. We're laid-back guys. We like to go out here and there, to the mall, to campus parties."
They talk football at home, but not a lot.
"We just try to get away from it a little bit," Jarrett said. "It's not a 24/7 thing. We have our own personal lives. We just laugh, joke around, play video games, just hang out like regular teenagers do."
With that, Jarrett caught himself, realizing Leinart is relative elder-statesmen. Leinart passed up a chance at millions of dollars last winter, deciding to stay in school rather than turn pro because he wanted to remain a kid for one more year.
Perhaps that's what Jarrett meant, although he did say Leinart is like a big brother to him.
The trust shared by the pair is evident on the field. While Leinart's accomplishments have been well-documented, Jarrett has quietly emerged as a star.
His 61-yard reception on a fourth-and-9 play set up Leinart's quarterback sneak TD with 3 seconds left that gave USC a 34-31 victory at Notre Dame on Oct. 15.
"I think that was one of my biggest plays so far," Jarrett said. "I felt a lot of pressure on me. I just went out and made the play. I think I'll always remember that catch."
He's not the only one.
Jarrett has 46 catches for 663 yards and 12 touchdowns this season, giving him 101 receptions for 1,512 yards and 25 TDs in 20 career games.
Mike Williams holds the USC career record for touchdown catches with 30 in 2002-03, and former Stanford receiver Ken Margerum holds the Pac-10 record with 32 in 1977-80. Jarrett could surpass both standards this year.
Keary Colbert holds USC's career record with 207 catches from 2000-03 and Johnnie Morton holds the career reception yardage record at 3,201 from 1990-93. Jarrett is nearly halfway to both.
"He's unbelievable. I think he's the best receiver in the country," Leinart said. "That's safe to say. He's dominant out there."
And to think, just a little over a year ago, Jarrett considered leaving USC because he was homesick. Leinart and his family had a lot to do with putting him at ease.
"When I first came here, his family were the first ones to open their arms to me, welcome me," Jarrett said. "Me and Matt already had a relationship. He was one of the guys who helped me make the transition from an East Coast guy to a West Coast guy."
With that, Jarrett said he was still an East Coast guy, adding: "I'm used to the West Coast. It's not as bad as I thought."
Jarrett, a 6-foot-5, 200-pounder, said Jerry Rice has always been his favorite receiver.
"As I was growing up, T.O. and Moss came along," Jarrett said, referring to Terrell Owens and Randy Moss.
Owens and Moss are great talents. They're also controversial. Jarrett appears to be anything but, although he's not lacking in confidence.
"I'm just a humble guy," he said. "I just feel like I'm blessed. God blessed me with the talent. I knew my capabilities ever since I was young. I knew I had a thing for catching the ball."
Jarrett has certainly impressed USC coach Pete Carroll.
"He is playing on a different level than we thought he would relative to where we saw him," Carroll said. "This is really one of the most natural catchers you can find now. He has marvelous hand-eye coordination.
"He is going to do some extraordinary things before it is all said and done."