As others have said, he's not great, but he's not terrible. He's a solid enough #5 starter. A guy you can skip over when warranted, but a guy who is going to put some decent innings together, while occasionally getting shelled for stretches. Its only ST, so don't worry too much about the results, they're meaningless. He's got a low vL rating and due to the expanded rosters of typical ST teams, teams could be stacking their lineups w/ lefty hitters on their ML team, as well as lefty prospects in their minors, not giving him the advantage he'd have of facing more righties in the regular seasons when rosters are set at 25. Can't say for sure, but I rarely look at the oppossing pitcher in ST, but set my lineups in a nature that I spread out my at bats to major leaguers and prospects thru the course of the entire spring training.
Season 22 was a "lucky" season, he won't be putting those numbers up again, but season 21 & 24 were more than respectable for a 5th starter, season 23, while not good, won't kill you. Set his pull count to 4, so when he starts to get hit hard, it will limit the damage. When things are going good, he'll stick around for longer stretches.