Louis van Gaal says Manchester United must win every one of their remaining nine Premier League games after Sunday's defeat to West Bromwich Albion.
Van Gaal had said a top-three finish was the target for United in his prematch interview with Sky Sports at The Hawthorns, but a 1-0 defeat has left them sixth, five points behind Arsenal in third and three adrift of fourth-placed Manchester City, who have a game in hand.
West Ham, meanwhile, are two points clear of United after their dramatic 3-2 victory over Everton on Saturday.
United's run-in contains matches against several of the Premier League's frontrunners, including Manchester City, Tottenham Hotspur and Leicester City, as well as Crystal Palace, Everton, Aston Villa, West Ham, Norwich City and Bournemouth.
Van Gaal said they now need to win every one of those games, saying after the match: "We need 27 points. It is a lot but it is always possible."
There had been optimism at Old Trafford after four successive wins in all competitions, but he admitted that losing to West Brom had been a "big blow" to United's top-four aspirations.
"You have always chances but I have said in advance -- these kind of matches you have to win, especially when you need to close the gap because you have lost too many games before," he added.