Manchester United beat Wolverhampton Wanderers 3-0 at Old Trafford on Tuesday to draw level on points with Premier League leaders Chelsea.
However, the Blues — who remain top on goal difference — will re-establish a points gap between themselves and reigning champions United if they avoid defeat at home to bottom of the table Portsmouth on Wednesday.
England striker Wayne Rooney put United, beaten at home by Aston Villa last weekend, ahead from the penalty spot in the 30th minute after Ronald Zumar handled Darron Gibson's corner and central defender Nemanja Vidic doubled the lead just before half-time when he headed in a corner that Wolves goalkeeper Marcus Hahnemann could only palm into the net.
Antonio Valencia's 66th minute half-volley made it 3-0 as Wolves dropped into the relegation zone.
Victory gave Sir Alex Ferguson a comfortable win in his 900th league match as United manager.
But Wolves boss Mick McCarthy, in what seemed an attempt to keep his best players fit for the more ‘winnable’ game against Burnley on Sunday, made 10 changes to the team that beat Tottenham last weekend, with Hahnemann the only survivor.
McCarthy could now find himself facing disciplinary action for breaking the League rule which requires clubs to field their strongest available sides.
“Wolves made life tough for us,” Ferguson said. “They had their second string out which wasn't surprising given they've got Burnley on Sunday.”
An unrepentant McCarthy added, “I made changes. I don't think we can do two nine out of 10 performances back-to-back then back-to-back again.
“I thought we were doing all right until the penalty went in.”
"On the back of a great performance on Saturday, this was very important for us."
Jerome gave Birmingham a 12th minute lead at St Andrews from just a yard out and the striker doubled the lead three minutes after the break.
New Zealand's Ryan Nelsen pulled a goal back for Rovers from close range in the 69th minute.
“I'm really proud of the players, it's fantastic,” said Birmingham manager Alex McLeish.
“It was a phenomenal performance and we could have won by more.”
In Tuesday's other Premier League matches, Villa leapfrogged Arsenal, who play Burnley on Wednesday, into third place with a 2-0 victory away to Sunderland, who had captain Lorik Cana sent-off for two yellow cards.
Cameron Jerome scored twice as Birmingham City beat Blackburn Rovers 2-1 for as the Midlands club won five straight top-flight games for the first time since 1973 to move up into sixth place.
Villa's England striker Emile Heskey struck from 10 yards after James Milner played him in following a lay-off from Stiliyan Petrov. And just after the hour mark, Milner made it 2-0 with a 25-yard shot.
“I'm delighted,” said Villa manager Martin O'Neill. “On the back of a great performance on Saturday, this was very important for us.”
Wednesday's other Premier League matches see Tottenham and Manchester City, both bidding to break into the top four, in action at White Hart Lane while Liverpool, struggling to hold on to their place among the leading quartet, are at home to Wigan Athletic.