Yes, that ipitcher will have problems with righties. But if he has a LOPS below .700 then this pitcher could still have some use.

If its a starter, and you know you are facing a team with 6 or more lefties(5 or more in N.L. besides the pitcher) in the starting lineup, then this pitcher should give you a decent start.

As a reliever at home you can make sure that he faces lefties at least twice as much as righties.