I know this comment was from a long time ago, but I just stumbled upon the Straker post today.
That was strange that he didn't get more of a shot, but he picked a bad time to get hurt. In 1988, he missed half of June, all of July and all of August,
Meanwhile, he had more competition than in 1987. That's not saying much - in 1987 they had Viola, Blyleven, Straker, and a bunch of guys who were truly awful. Mike Smithson with a 5.94 ERA was the #4 starter. In 1988, they still had Viola (won the Cy young) and Blyleven (not good, but he really wasn't fighting Straker for a job.) Add Allan Anderson, who led the league in ERA, and Straker is fighting to keep the 4th or 5th starter slot. That competition was quite a bit better than 1987 - Charlie Lea and Freddie Toliver weren't great but they were OK. Roy Smith made four starts and was OK, too. (He was better in relief.) Straker was slightly better than them, but it was a group of guys who were basically interchangeable, and Straker had the bad luck to get hurt.
In 1989, they added a few more interchangeable parts - Rawley, Dyer, Guthrie started a few games, Smith was better and was in the rotation.
And then the Viola trade happened, which brought back Aguilera (a starter at the time), Tapani, and West (supposedly the key acquisition/best prospect). That buried Straker - his 4.24 ERA in the PCL was better than it sounds - a lot of those stadiums were launching pads.
And then he pitched 6-2/3 innings in AA and disappeared.