He has not pitched badly at all - I just looked up his game log for the season - he has pitched 22 IP (small sample size as boogerlips states, but for a RP that might only go 40 or 50 it is legit to ask) in 32 games.
He has given up 20 ER all told, but 10 of those have been in his last 4 pitching appearances, totaling 0.2 IP. That is why his ERA is so high, those 4 appearances. Not sure why he has suddenly take to giving up so many runs but perhaps those 4 opposing teams had better hitters than the ones he had faced previously. It does not appear to be pitch count, given the low IP total in those games, and he is listed as having been at 100% for each.
So it is just a slump. Before that he had pitched in 21.1 IP with 10 runs given up, not great, but not horrible.