He started his career in 1996 after facing one batter the prior season. It took until the 1997 season before he solidified himself as the Astros closer finishing with 23 saves but 106 Ks in 66 1/3 IP. After notching 30 saves the following year, he had an all time season for Houston in 1999, finishing with 39 saves, 1.57 ERA, 127 Ks in 74 2/3 IP. After an injury would hold him back the following season, he added 39 and 35 saves the two subsequent seasons. 2003 would see him notch a career high with 44 saves, with a 1.78 ERA and 105 Ks in what was also a career high 86 IP.
After that he took his talents to Philadelphia. A lopsided trade (another one with the Astros and Phillies) sent him to the Phillies for Ezequiel Astacio, Brandon Duchworth, and Taylor Buchholz. He may have ran his mouth the most in Philadelphia, but he certainly produced. After injuries shortened his first season there, he had 38 saves, a 1.51 ERA and 87 Ks in 77 2/3 IP for the Phillies in 2005. He joined the Mets the next year, notching 40 saves, and getting the Mets to the playoffs. After he was traded from the Mets to the Red Sox, he signed with the Braves and finished with a bang. 2010 he was 7-2 with a career low 1.43 ERA, 37 saves and 104 Ks in 69 2/3 IP.
Two things hold Wagner back. Number one is his injury history kept his stats from being legendary. He lost a lot of time in 2000, 2004, 2007 and 2008. He was also a terrible postseason pitcher. He gave up 4 runs in 3 games (3 IP) for the Astros in 1997-1999. He was beaten up by the Cardinals in the 2006 NLCS for the Mets and gave up runs in both of his appearances for the Boston Red Sox in 2008. An injury forced him to walk off the mound for the Braves in 2010 postseason.
Though he, or no one else for that matter, is in the same class as Mariano Rivera, Wagner has a good chance of making the Hall of Fame. His 422 saves rank 5th all time trailing only Rivera, Trevor Hoffman, Lee Smith and John Franco. A seven time All Star, had 4 seasons with an ERA under 2.00 and 4 seasons notching 100 or more Ks. I say his stats speak for themselves. The only drawback is Hall of Famers like Dennis Eckersley, Bruce Sutter, Goose Gossage and eventually Rivera all had postseason success, something Wagner did not have. Nonetheless, I think he will be a Hall of Famer.