More importantly United, who were 18 points adrift three weeks ago, have now reduced Chelsea's lead at the English summit to nine points with seven games remaining.
Ferguson is refusing to give up the chase for the title until it is mathematically impossible. His side face Jose Mourinho's leaders on the penultimate weekend of the season and there is growing belief in the United camp that they can further reduce Chelsea's cushion before they visit Stamford Bridge on April 29.
They moved five points clear of third-placed Liverpool in the race to qualify automatically for next season's Champions League without the services of several key players.
There was no Gary Neville or Kieran Richardson while Mikael Silvestre, Ryan Giggs and Louis Saha were all relegated to the substitutes bench as Ferguson made five changes to the side which started the 3-0 win over Birmingham three days earlier.
Injury denied Neville his 501st outing for the club, the England defender's absence paving the way for Gerard Pique to make his first Premiership start.
Pique did not let himself down, the young Spaniard producing a mature performance beyond his teenage years. He forced West Ham's Shaka Hislop into his first serious save before playing a key role in the winning goal.
Van Nistelrooy's 149th goal in a United shirt was probably one of his sweetest as he released almost six weeks of pent-up frustration in one clinical moment.
This was not vintage United by any means as West Ham made life difficult for the hosts. Alan Pardew's side have enjoyed a successful first season back in the top-flight. Not only have they established themselves in the top-half of the table but the London club have also reached the semi-finals of the FA Cup.
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