Oscar scored the only goal of the game with a stunning strike as Chelsea beat Stoke to book an FA Cup fifth round tie with Manchester City on Sunday.
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"Juan Mata is an absolutely fantastic player, and more than that he is an absolutely great lad," Lampard told ITV. "[I] wish him all the best personally.
"The difficult thing here is that there are so many quality players and Oscar has been fantastic this year, as has [Eden] Hazard.
"Willian's shown that, and we've got so many riches in that position that it's difficult, but you need performances like that from Oscar today [Sunday]. That free kick was absolutely top drawer."
Lampard is anticipating a strong finish to the season, now that the squad has bought into the philosophy of returning boss Mourinho.
"There's a good feel around the place, [with] the manager coming back [it] took a little bit of time for him to get his points across, I think," he said.
"In the last couple of months we've been finding that little bit of mentality - that feeling in the dressing room - and we're going out there with more confidence.
"We have to keep that up - the minute you drop that, the results will turn - so we have to make sure we keep at it and carry on this form."