In short, other relievers often control what becomes of the runners you put on base, while a lot of the runners you let score might technically go on somebody else's ERA. All a pitcher can do is keep guys off the bases. Strike guys out, don't walk them, don't give up homers, and get lots of grounders. When you allow an 800 OPS, and have a 1.48 WHIP, you just aren't pitching all that effectively. FYI, I'm not saying he was terrible or anything, he was a mixed bag, which is what happens with most relievers.