Garver could have been the first guy up for any injury to a catcher, Mauer, Morrison or Grossman. He would have had his opportunity.
And don't misinterpret that I am unhappy that Garver started the season in the majors. I am not. The reality is that the Twins were only able to get a Wilson type to stash in Rochester and that lack of depth is an issue now. That is the price of putting guys with options in the majors to start the season and not getting solid veteran backups.
Would he actually have an opportunity though? This is likely to be the first season Castro plays fewer than 100 games since he entered the league. If Mauer, Morrison, et al get injured, the front office likely turns to someone with more defensive acumen because the plodding hitters are interchangeable.
Go with your best 25. Garver is one of those guys and he earned his place in Minnesota. Deal with injuries if and when they happen.