By JANIE McCAULEY
The pitcher's agent, Bob Garber, confirmed the decision and said Oswalt would go to work for his agency, RMG Baseball. Oswalt will be vice president of baseball operations.
"Roy is now going to be representing players with me," Garber said Tuesday night. "He's now an agent."
The 36-year-old right-hander had a 163-102 career record with a 3.36 ERA. Oswalt won 20 games in consecutive seasons (2004-05) with the Houston Astros and was the 2005 NL championship series MVP. He pitched more than 200 innings seven times but was hampered by injuries in recent years.
"He was a tremendous competitor," Giants right-hander Matt Cain said. "He was one of the guys I always loved to watch pitch. I remember facing him for the first time and I knew if I gave up more than a couple runs that it wasn't going to be a good day for us. He went about his business every fifth day like a true pro."
Oswalt got hurt with Houston on June 11, 2003, when he and five other pitchers combined to no-hit the New York Yankees in an 8-0 victory in the Bronx. It was the only six-pitcher no-hitter until Seattle did the same thing against the Dodgers on June 8, 2012.
Oswalt strained his right groin and left in the second. He looked toward catcher Brad Ausmus after his second pitch of the inning, his 23rd of the game, and immediately was replaced.
The Yankees had gone 6,980 games -- the longest streak in major league history -- without being no-hit, since Hoyt Wilhelm's 1-0 victory for Baltimore on Sept. 20, 1958.
Oswalt was 0-6 with an 8.63 ERA in nine outings and six starts for Colorado last year. He signed a minor league deal with the Rockies in May 2013 and missed time with a strained left hamstring.
Texas Rangers manager Ron Washington was thrilled to acquire Oswalt in the middle of the 2012 season, when he went 4-3 with a 5.80 ERA in 17 appearances with nine starts.
He joined the Rangers on June 22, 2012, but didn't know if the team just planned to trade him away. Washington often said Oswalt "has been a pro" in handling a tough, unclear situation that called for him to be used primarily out of the bullpen.
That was after Oswalt spent two stints on the disabled list during 2011 with Philadelphia because of lower back inflammation. He went 9-10 with a 3.69 ERA in 23 starts for the Phillies that year, and his 139 innings were his fewest since 2003. He didn't go more than 59 innings in his last two years.
A 23rd-round pick by Houston in the 1996 amateur draft, Oswalt pitched his first nine-plus seasons for the Astros (2001-10) and then played for Philadelphia (2010-11), Texas (2012) and the Rockies (2013).
On Aug. 25, 2010, Oswalt became the first Phillies pitcher to play a position in the field in 39 years after Ryan Howard was ejected in the 14th inning of a 4-2, 16-inning home loss to the Astros. With the Phillies out of position players, Oswalt went to left field and Raul Ibanez took over at first for Howard.
Oswalt drew a rousing ovation from the crowd when he caught a routine fly ball. He was the first Philadelphia pitcher to play a position since Bill Wilson on Aug. 6, 1971.