Two goals apiece from former Red Devils defender Jonathan Spector and England striker Carlton Cole put paid to the visitors at Upton Park, as the Hammers lifted the gloom of a poor league season to date.
Grant commented:”I thought we could win, but this is still an unbelievable result. We continue our progress.
“We scored four goals and could have scored more, but for me four is enough.
“To be in the semi-finals is very good for this club. We are trying to build something step by step. We have done the right thing.
“We have played many more good games without winning, so the players maybe have lost confidence. But the most important is to show mental strength and tonight was unbelievable.
“The gap at the bottom of the Premier League was five points and is now three points. We have many games left and I’m sure that this shows we can be good in the future.”