During a conference call Monday, Indianapolis Colts offensive coordinator Nick Sirianni told reporters Rivers was sold on the strength of the team's offensive line.
"The big part of Philip being here is Anthony Castonzo. Quenton Nelson. Ryan Kelly. Braden Smith. Mark Glowinski," Sirianni said (via NFL.com's Nick Shook). "Those guys are studs.
"That's something that he just kept mentioning after we signed him, of how valuable those guys were to him."
The Colts tied for the ninth-fewest sacks allowed (32) in 2019, which can be partially attributed to Jacoby Brissett. Football Outsiders ranked the line seventh in adjusted sack rate, and Pro Football Focus placed the unit third in its year-end rankings.
The raw sack numbers might have been better with somebody else behind center.
Speaking with the Indianapolis Star's Joel A. Erickson in December, Sirianni said Brissett held on to the ball too long in the pocket.
"We preach it to him, 'Hey, when you take a five-step drop or three-step, and when you hit that top and you hitch and throw, your mind has to be made up,'" he said. "'Because there are these guys on the edge that are coming.'"
The numbers back up why Sirianni might have felt frustrated. According to NFL.com's Next Gen Stats, Brissett's average time to throw (2.9 seconds) was the second-highest in the league. Rivers, meanwhile, had the fifth-fastest release (2.6 seconds).
Rivers' quick decision-making helped the Los Angeles Chargers allow 34 sacks, 11th in the NFL, a stark contrast to their position in the PFF hierarchy (29th). That could also explain the eight-time Pro Bowler's 20 interceptions, which tied for his second-most in a season.
Things should be a lot easier for Rivers as he makes at least one more run at a Super Bowl title.