They both were sought after prospects in the 2011 NFL Draft.
They know each other well, and even swapped jerseys after the San Francisco 49ers defeated the Arizona Cardinals 23-20 in the '13 regular season finale.
So even after a four-turnover outing against the Chicago Bears, it comes as no surprise that 49ers signal-caller Colin Kaepernick is still being complimented by Patrick Peterson, Arizona's top cornerback.
"Kaepernick is a great quarterback," Peterson said this week from inside the Cardinals locker room. "Games like that happen. It's all a matter of how you bounce back from them. We just can't have him bounce back and have a great game against us."
If Peterson and the Cardinals are able to defeat Kaepernick and the 49ers on Sunday, it would be the cornerback's first victory over his friend.
Kaepernick has enjoyed tremendous success against Arizona, the NFC West's current first-place tenant.
San Francisco's fourth-year passer has three wins as a starter against the Cardinals. He's also posted a 106.4 passer rating with six touchdown passes and one interception against Peterson's defense. When Kaepernick starts and has a 100-plus quarterback rating, the 49ers are a perfect 14-0.
That was the case in Week 1 when Kaepernick posted a 125.5 rating, completed a pair of touchdown passes to tight end Vernon Davis and San Francisco soundly defeated the Dallas Cowboys on the road. Last week, however, the 49ers lost a 17-point lead and committed uncharacteristic turnovers in the second half, including two interceptions by Kaepernick to Bears rookie cornerback Kyle Fuller.
As for Peterson, Arizona's respected cornerback has never intercepted Kaepernick. Moreover, Peterson has yet to record an interception, or a pass breakup, this season. Perhaps the stats are an indication of his status as one of the game's top shut-down defenders.
"He's a great player," Kaepernick said this week. "Has all the physical tools you'd want in a corner."
Peterson is the headliner on a Cardinals pass defense that ranks 17th in the NFL, allowing 218 yards per game. Arizona's defensive line will have a big role in limiting Kaepernick's production. According to Peterson, Arizona won't sit back and let Kaepernick face a four-man pass-rush this week.
"Being a team that we are, we pressure a lot," Peterson said. "We're going to get after him a little bit and see what happens."
Kaepernick was sacked four times last week against the Bears. The Cardinals have sacked Kaepernick four times in their past three meetings.
"We have to make sure we keep him down," Peterson said. "As a defense, we understand what type of quarterback Kaepernick is. He's a play-maker. He has a strong arm. He can make plays with his legs and his arm, so we have to make sure we stay plastered in our coverage and make plays on his receivers."
With a one-game lead over the 49ers, Seattle Seahawks and St. Louis Rams, Peterson and the Cardinals understand the importance of Sunday's matchup.
"Although this game is early, we can hold a tie-breaker," the cornerback said. "Any time you can beat your divisional opponent, it's huge, especially when you can do it this early.
"The way this season is going, it's a big game. Playing these guys, this game is early, but it means a lot."