With an FA Cup replay against Chelsea 48 hours after their trip to Wearside, the Red Devils are expected to rest players but the Black Cats boss is still expecting a tough test
The Black Cats face the league leaders, who have a 15-point gap over second-placed Manchester City, in the early game this weekend as they look to distance themselves from the relegation zone.
Sir Alex Ferguson’s men take on Chelsea in an FA Cup replay two days later, but O’Neill believes even if the Red Devils boss rests players they will still be a massive test.
“Manchester United have been the best side in the league this season,” he told Sunderland’s official website. “They’ve come from behind in matches to win, and won a lot of games.
“They are well clear in the league with some big games coming up. Whatever side they put out will be capable of winning matches, as has been proved year in, year out.
“But it’s about what we do ourselves. We have some matches to win. There are games coming up which are difficult on paper, but we should look forward to them.
“We need to win games and the sooner we do that the better.”
O’Neill is without striker Steven Fletcher and captain Lee Cattermole for the rest of the season but the 61-year-old is not ready to make excuses and sees it as a chance for Sunderland's other players to make an impression.
“Obviously it’s not great, but it’s something we have to get over,” he added. “Injuries are inevitable over the course of a season, though they’ve come at a bad time for us.
“It’s a blow, but there’s nothing that can be done about it.
“Other people now have an opportunity to go and play in some really big games. There’s some fantastic matches and a chance [for players coming in] to show their mettle.”