John Sullivan is doing his best not to complain about his luck -- although that might be getting more difficult.

The center missed almost all of training camp because of an injury to his right calf and then injured his left calf on the first play from scrimmage in Week 3 against Detroit. Sullivan did not play last Monday night against the New York Jets and, although he's listed as questionable for Sunday's game against Dallas, it's expected he will sit out again.

"It stinks," Sullivan said. "I'm not going to say it doesn't. But at the same time getting negative and not having a positive attitude just isn't the way to go about getting better. So I'm in here in the training room and getting back out there at practice, trying to do what I can for right now. We'll get back out there eventually. Sullivan took over as the Vikings starting center last season after Matt Birk departed as a free agent for Baltimore. Sullivan was the starter for all 18 games, including playoffs, but this year the Vikings have started two centers in four games and it will be three in five if Jon Cooper starts on Sunday against Dallas. "There's nobody to blame [the injuries] on," Sullivan said. "It's not anybody's fault. It's just the way it is. I can't put my finger on it and I wish I could. We're doing our best to fix it." Meanwhile, Sullivan said he is doing everything he can to help Cooper, who was signed as a rookie free agent from Oklahoma last season. "I try to point stuff out all the time," Sullivan said. "Stuff that I'm seeing, I'm watching tape. Little tells that the defense gives away. Kind of a mindset on a certain play, what we want to do in certain situations. Aside from what [offensive line coaches] Pat [Morris] and [Jim Hueber], how they're coaching it. Just try to give them a little bit from another player's perspective."