After 15 solid yet injury-filled seasons, quarterback Trent Green retired Friday.

Green’s legacy might not be for his play on the field — he had a few decent seasons with the Chiefs — but the knee injury he suffered in 1999. Had he not gotten hurt that preseason, the world may never had known who Kurt Warner was. But Warner stepped in and began a possible Hall of Fame career, while Green slipped into the second tier of NFL quarterbacks.

It’s interesting to postulate what Green might have done in 1999 had he been healthy. He retires with a Super Bowl ring and 162 career touchdown passes — not too shabby. Unlike many other what-if QBs, Green is leaving the game after a successful career.