He didn't look great in that game and didn't do much with the puck, but he didn't look wholly out of place either. Apparently everyone else viewed it as a miserable performance.
It's not that he played miserably but that he didn't excel in the areas that are supposed to be his strengths. The folks who were thinking "the only thing holding Sheahan back is his production" realize that he has to develop in other areas as well so he's slipped a bit in their rankings.
The same thing happened during Nyquist's and Tatar's first call-ups. "Why Nyquist dangling/setting up plays like we were told he would?", "Why isn't Tatar driving to the net and potting goals?" Last season they both started to show their strengths and I'm sure Sheahan will as well so long as he avoids injury.