RVP's late leveller rescues United
Manchester United striker Robin van Persie came off the bench to score the late equaliser that salvaged a 2-2 draw at West Ham and prevented his side from becoming the biggest casualties of the FA Cup third round.
With Alex Ferguson's side trailing in stoppage-time, van Persie combined with Ryan Giggs to produce a sublime equaliser that denied West Ham a famous Cup upset in Saturday's clash at Upton Park.
United had taken a first-half lead through Tom Cleverley's well-struck effort but it was not long before Wales defender James Collins headed home a Hammers equaliser.
Collins looked set to be the unlikely hero when he scored again with another header in the second half, but former Arsenal star van Persie had the last word to earn a replay at Old Trafford later this month.
Ferguson had made a number of changes to the United line-up after Tuesday's 4-0 win in the Premier League at Wigan.
Nemanja Vidic, Paul Scholes and Shinji Kagawa were among those handed starts as van Persie and Giggs dropped to the bench.
The West Ham line-up had a new look to it as well, although Joe Cole's was a very familiar face to the Upton Park faithful as the England midfielder played for them for the first time in almost 10 years.
Cole, who had left the Hammers for Chelsea in 2003, this week ended an unhappy 18-month spell at Liverpool to rejoin the club where he first made his name as a teenager.
West Ham almost took an early lead when Alou Diarra rose to meet Mark Noble's corner, but Scholes was there on the line to block.
Danny Welbeck had a goal ruled out because United teammate Javier Hernandez was offside and West Ham defender Dan Potts booted a header from Vidic off the line moments later.
United took the lead in the 23rd minute through Cleverley, who arrived unattended at the back post to curl the ball past Jussi Jaaskelainen after the home defence had failed to cut out a cross from the right from Hernandez.
The lead was short-lived however as Joe Cole's ball into the box four minutes later was perfect for Collins to send a powerful header past David de Gea.
United were crest-fallen for a while but Welbeck did well to sprint away from a posse of challengers before launching a shot that was well saved by Jaaskelainen.
West Ham replied with a spell of pressure before the break that saw United struggle to cope with a succession of set-pieces, with Vidic finding the physical Carlton Cole a real handful.
Cleverley fired the first chance of the second half over before Carlton Cole was on the end of a cross from namesake Joe. For a moment it looked as though he had scored only for de Gea to make an acrobatic catch.
The Spaniard had no answer to the home side's next attack - and again it was that man Collins linking up with Joe Cole to do the damage.
Cole cut in-field from the left and crossed for Collins, given too much space by United's defenders, to glance a fine header into the far corner of de Gea's net.
Van Persie replaced Hernandez with 23 minutes remaining and the Dutchman immediately headed wide from a corner.
Then Alexander Buttner's cross from the left should have resulted in a United equaliser but Welbeck headed over from all of five yards.
Joe Cole, who had taken a bang on the nose, was cheered off when he was substituted 12 minutes from time but the Hammers were unable to see the game out without him.
Substitute Giggs headed a good chance over as United pressed forward for an equaliser.
But Giggs made amends in stoppage-time with a superb 50-yard ball over the top of the West Ham defence that saw van Persie take a majestic first touch before sprinting away from James Tomkins to bury a low shot past Jasskelainen.