Coppell claimed he was not that shocked when United lost at Coventry and believes they could be hampered in the new year by fixture congestion as they chase trophies on three fronts.
"Blackburn are a realistic possibility given the quality and depth of their squad," he said. "You can say they more than anyone else have the best chance of pushing United all the way to the wire. Blackburn can play badly and still pick up points, which is a good sign.
"When games come thick and fast, that's when surprise results like United's defeat at Coventry happen. With all the internationals and European Cup matches coming up, that's the only way I can see Manchester United losing it."
Coppell claimed he is not too surprised by Rovers' transformation from candidates for the drop to contenders for the top under Roy Hodgson, but he admitted he had not expected Hodgson, with his European coaching background, to use a 4-4-2 formation with wingers.
"All credit to Blackburn - they are the surprise side of the season," Coppell said. "Everyone expected an improvement under Roy but nobody expected them to be as `English' a side as they are."
Much has been made of Chris Sutton's form this season but Coppell picked out Kevin Gallacher as his key man for Rovers. Gallacher took his goals tally for the campaign to 11 against Palace in their 2-2 draw at Ewood Park and Coppell felt he was outstanding.
"I think Blackburn's catalyst has been Kevin Gallacher," he said. "Chris Sutton's obviously a top-quality striker but Gallacher drops off so well and I feel he's the one who makes things happen. We tried to go tight on him, but given the quality of his play he still got strikes on goal and scored."
Damien Duff's fame has already spread to south London but Coppell prefers Jason Wilcox, who has lost his place to the teenage Irishman. "I know all about Damien Duff and what he can do, but I personally like Jason Wilcox as he never lets you down," he said. "Duff has more subtlety about his play but that is allied with inexperience. In matches, that can count against you, but Wilcox has experience."
Milan's Liberian striker, George Weah, will have to have surgery on a spinal disc injury and is expected to be out of action for at least two months. He last played a Serie A match for Milan against Bari on 7 December. He has scored only three goals in 11 games this season, often complaining of back pains.
The French international midfielder Christian Karembeu moved a step closer to joining Real Madrid yesterday, according to reports on Spanish state television, TVE, which said Real's president, Lorenzo Sanz, met his Sampdoria counterpart, Enrico Mantovani, for negotiations.
The two clubs teams are believed to have reached an agreement after several months of negotiations, with Real paying a pounds 2m for the Frenchman.