Albion have garnered just five points from their five league games but they were impressive 3-0 winners over Sunderland last time out, a result they can build on, according to Clarke.
"I never understand why people would ask a professional whether they're going to win or not," he said. "As a professional, I think I'm going to win every single game I go into. If I don't think that, how can I convince the players?
"And I hope every player I've got goes to Old Trafford with the same feeling as me - that we can win.
"It's a game where the pressure is not on us because everyone expects Manchester United to beat us. But that doesn't mean we don't expect to go there and do well.
"Maybe 99 per cent of the country doesn't expect us to go there and do well. But we expect to go there and get a good result.
"We don't go there with any fear. We go there with positivity and we go there to try to get a result, looking to put on a good performance, we go there trying to win. We need more points on the board.
"We used the squad well in midweek and had a good performance, and now I can use the squad again at United.
"That's why you ask for a big squad, so you can rotate and keep players fresh for certain games.
"I made eight changes in midweek, and there will be six or seven changes, I would imagine, going into the weekend."