Steam gave award walk off homerun
 

I was playing out a game and with no one on base and two outs I hit 1 for next pitch and before anything happens a little alert pops up from the steam client showing an award notification of walk off homerun and then the action proceeded.

Talk about a complete buzz kill on what was a really good game...

I know it's not funny but that's kinda funny.

If you press shift + tab while playing, the steam overlay will come up, and it'll have an option there to disable it (or if not, right-click on OOTP from your games list, select 'preferences' and you should be able to disable the steam overlay from there). I'm not sure if that'll also get rid of the new achievement display, but it could.