Casey Fossum should have been given the start tonight. Yes, he didn't do all that well either, but what the pitchers actually did in the game is irrelevant. The manager should be putting the team in the best position to win games; by putting the inferior pitcher as the starter and the superior one as the primary reliever Lou put the team in a risky position, giving the more important job to the pitcher less likely to do well.
Fossum was once a highly touted prospect and rightfully so, continuing his minor league success into the majors with Boston in 2002, having a solid 100 inning performance with the peripherals to match. After the trade to Arizona he collapsed, apparently mainly due to a shoulder injury that he is just now getting fully recovered from. So far this season he had been excellent in relief, making a strong argument for being the best pitcher on the staff up to this point. Considering that he was previously a starter it should have been a no-brainer to use him for the spot start unless they had some other excellent candidate to use instead. Making the excuse that Lou "doesn't want to mess with the bullpen" is ridiculous...if you want the bullpen to do a good job then use the best starters you have available so you can protect them.
So who's this guy that the Rays think is a better starting option tonight than Fossum? John freakin' Webb. A mediocre "prospect" with all the upside of a generic right-handed middle reliever. He looked like a good prospect back in 2002 when he was still in the Florida State League but since he made it to AA he has not had a good strikeout rate or above average control. He hasn't shown any particular ability to prevent home runs at an above average rate. Out of the three things pitchers have the most control over he isn't overly skilled at a single one. He's almost 26 years old, there's no reason to think that he's going to suddenly put it together this season. Maybe he will one day but up to this point he hasn't shown anything to make a reasonable evaluator of talent think he's going to be a good starting pitcher.
Sure, it's one decision in one game and it might not have mattered anyway. But this isn't an outlier, it's yet another decision based on very shaky reasoning that puts the Rays in a less advantageous position to win a game. This is not a good team, they need every edge they can get but they aren't being allowed that.