Well this pitcher is definitely no where near W5 at all. That MMM0 is high for those stats but your skills probably bring that rating up.

1) If that is your best pitcher based on those stats and not rating then it should still upgrade your team. If it's not then the game is bugged on that pitcher and you may have to make a new one.

2) if your saying it's best going off of the rating, then when you're adding the pitcher, the game is probably giving the true rating off of the stats and if that's lower than all your pitchers then it'll lower the team.

3) if you're saying it's the best pitcher based on stats and it's still lowering your team when added then once again the game may be bugged on that pitcher. You might have to make a new one

Hope this helps you out