Reich has history with Rivers. He was his quarterbacks coach for a season and then his offensive coordinator for two seasons with the Chargers.
"Just being there on the inside in the three years that I was and knowing the quarterback position like I do, I was so confident physically he was the right player and he had not lost anything," Reich said Tuesday. "I didn't notice any physical gifts diminishing. From a locker room guy, this guy brings juice ... When I tell you he's elite intellectually, he's at the top. There are a group of guys in the football world I would put in that category -- not everybody gets those gifts. He has them."
Reich had his eye on Rivers since it became known that the quarterback would become a free agent for the first time in his 16-year NFL career earlier this winter. The coach mentioned his interest in Rivers to general manager Chris Ballard and owner Jim Irsay because he believes the quarterback has what it takes to get them back to the playoffs.
The coach got his new starting quarterback when the Colts signed Rivers, 38, to a one-year, $25 million deal.
"Went back and looked at all his film for the last two years and didn't see any physical drop-off in his play, so this was an unique opportunity," Reich said. "It wasn't so much about what Jacoby [Brissett] wasn't doing. It was about an opportunity someone we feel is an elite quarterback and can help our team."
Rivers' signing ended one of the worst-kept secrets around: that the Colts were going to look to upgrade the quarterback position if the opportunity presented itself. Brissett had started off strong but sputtered dramatically at the end during his first season as Andrew Luck's replacement in 2019.
Brissett was 30th in the NFL with a completion rate at 60.8% as the Colts finished 7-9 and missed the playoffs for the fourth time in five years.
Reich called Brissett, who is headed into the final year of his contract, to give him the heads-up that it appeared that they were going to sign Rivers.
"Honestly, he wasn't happy about it," Reich said. "But he's a great teammate and a great leader, and I'm sure he'll be good. Even though Jacoby isn't a starter, but there's nothing saying he can't play ... We're wide open. [Offensive coordinator] Nick [Sirianni] and I have been talking: What does it look like if Jacoby plays five plays a game? Seven plays a game? We're open to that."
Sirianni spent five seasons with the Chargers, including two as their quarterbacks coach. Colts tight ends coach Jason Michael also spent time on the Chargers' coaching staff. Reich said Rivers may know more than 85% of his system since the quarterback has run the same one since 2013.
Rivers, who has started 224 straight games, has thrown for 59,271 yards and 397 touchdowns to go with eight Pro Bowl invitations in his career. He became the first player in league history to have five straight games with a passer rating of 120 in a single season in 2014.
Rivers is joining a team in Indianapolis that's returning an offensive line that started all 16 games last season -- the only team in the NFL to do so -- and a rushing attack that finished in the top 10 in the league.
What the Colts can't put up with from Rivers is interceptions. His 20 interceptions were the third most in the league last season.
"That's unacceptable, and he knows that," Reich said. "Twenty is never good under any circumstance. We want to reduce that number. We think we have the right team around him to get that number down to where it needs to be."