Number 3: Roy Oswalt
The next player on this list is Roy Oswalt, another former Astro. One of the issues the Rangers have made throughout the years is signing former Astros. The only two I can think of that had success in Arlington after playing in Houston are Nolan Ryan and Hunter Pence.
Oswalt had been a dominant pitcher for the Astros in the mid-to-late 2000s time period. From 2001-2008 he won 129 games. He finished top 5 in Cy Young voting in five of those seasons. He was one of the best pitchers in the National League. After more than a decade of playoff appearances and a World Series appearance, the Astros chose to tear it and traded Oswalt in 2010 to the Phillies.
He became a free agent and as the 2012 season got underway he still was a free agent. Finally at the end of May he signed with Texas for 1 year and $5 million dollars. Oswalt made his first start on June 22nd and was good. He pitched into the 7th inning giving up only one run and striking out six. That would be the high point though. He made five more starts before being moved to the bullpen. He gave up five runs in his next start, nine earned runs to the White Sox in the start after that, and then ended the month of July with a start giving up eight runs to the Angels.
The issue plaguing Oswalt was that he was very hittable. The stuff that blew hitters away earlier in his career no longer did. He was much better when he came out of the bullpen. Having to only maintain his stuff for two innings rather than five or six worked out better for him.
The 2012 Rangers ended up collapsing down the stretch and lost the division title in game 162 to the Oakland A's and then lost a one-game playoff to the Baltimore Orioles. The Rangers after two consecutive World Series ran out of gas by the end of the 2012 season. Oswalt would pitch one more season in Colorado before signing a one-day contract with the Astros and retiring with Lance Berkman. He had a great career and even though the signing made sense at the time it did not end up working out for Oswalt or the Rangers.