Pitching, beyond question, is the name of the game. Rasmussen has thrown 73 pitches, has no one on base, and Cash has someone warming up--he just came in after Vazquez singled.
The 3 best teams in the AL-- the Yankees, Astros, and Rays--also have the lowest team ERA's. And the A's ERA is 4th best and the White Sox 5th best.
The Sox ERA is 8th best. I do not see any way the Sox are going to get into the playoffs. I also don't mind admitting that the ERA is bad in part because the defense is bad. Errors aren't the problem because they lead to unearned runs, which don't count against pitchers. The problem is with plays which should have been made but aren't--and also don't involve charged errors.
So, yes, poor defense is a factor, but the last 2 games were lost because of rotten pitching.