Manchester United struck through Robin van Persie in stoppage time to secure a 2-2 draw at West Ham United and forced a replay of their FA Cup Third Round tie, on Saturday night.
Jonny Evans had to scramble the ball clear in the 11th minute while Potts had to clear off the line at the other end eight minutes later after Nemanja Vidic had powered a header at goal from a corner.
United would then hit the front in the 23rd minute when Javier Hernandez burst down the right before cutting back for Tom Cleverly who buried a superb finish.
The lead lasted just four minutes though before new boy Joe Cole whipped in a superb cross which James Collins got up to meet with a header.
Kevin Nolan saw a penalty appeal turned down in the 31st minute while Danny Welbeck had his strike from a tight angle parried by the goalkeeper.
Cleverly fired a wild shot over the crossbar three minutes into the second period but the Hammers would stun their opponents in the 59th minute when Cole curled another great cross in from the left and Collins tucked away an almost identical goal.
Welbeck had a great chance to pull the game level in the 73rd minute when Welbeck got up to meet a cross from Alexander Buttner but he nodded over from close range.
West Ham could have killed off the game in the 88th minute but Carlton Cole couldn't hit the target under pressure from David de Gea and that would be punished in the second minute of stoppage.
Ryan Giggs put a fantastic ball over the top which Robin van Persie controlled brilliantly before lashing a low shot past the goalkeeper.
United tried to snatch a late winner but they were unable to produce a finish as the game ended in a stalemate.