McCown, 40, announced his retirement from the NFL in June, before coming out of retirement to sign with the Eagles in August. The 17-year veteran was forced into action during Sunday's game after Eagles starting quarterback Carson Wentz sustained a concussion in the first quarter at Lincoln Financial Field in Philadelphia.
McCown completed 18 of 24 passes for 174 yards in the 17-9 loss. The Eagles quarterback hugged his teammates as tears streamed from his eyes after the game. He told reporters he became emotional because of the "finality of playoff football" and "just being done and not getting it done."
McCown was making the first playoff appearance of his career.
"I'll probably reflect on that [the playoff appearance] later," McCown said, as his voice cracked. "Again, it's probably with a sour taste, but I'm thankful. My wife and family have moved around a lot and have been there for me. To go out there and get to play in a playoff game was special.
"I can't thank them enough for their support. It was a heck of a ride. I left it all out there, I know that much. It is different playing at 40. Your body talks to you a lot. I'll reflect on that later, but it was fun to be out there for sure."
McCown began his career as a third round pick by the Arizona Cardinals in the 2002 NFL Draft. The Southern Methodist University product played four seasons for the Cardinals before tenures with the Detroit Lions, Oakland Raiders, Carolina Panthers, Chicago Bears, Tampa Bay Buccaneers, Cleveland Browns, New York Jets, and his initial retirement. McCown also spent a season away from the NFL in 2010, playing for the UFL's Hartford Colonials.
The Eagles quarterback has 17,731 yards, 98 touchdowns and 82 interceptions in 102 NFL appearances. McCown owns a 23-53 record as a starting quarterback.
McCown said he didn't know yet when asked if he was going to retire for a second time following the playoff loss.
"This year has been nothing short of special for me," McCown said. "I've really enjoyed it and have learned so much from so many people. I'm thankful to be a part of it.
"As far as the future goes, we'll see. I haven't made any decisions yet. I'll get with my family and talk with them. I retired once, so I know how to do that. We'll just see. I don't know yet."