Mata's arrival at Old Trafford has offered a boost to a United side struggling for confidence and form this season, with the Spain international signing from Chelsea for a club-record £37.1 million during the January transfer window.
Giggs insists Mata has what it takes to make the grade at United and when asked if he could become a United great, the Welshman told MUTV: "I think he could be.
"He's obviously got the talent. I don't want to put too much pressure on him but I don't see why not."
Saturday's 2-1 defeat at Stoke on Saturday means United remain seventh in the table, seven points adrift of a UEFA Champions League place.
But Giggs feels a major signing such as Mata can offer a massive boost to David Moyes' side, with the 25-year-old having already settled into the side.
"The players are just like the fans," added Giggs.
"When they see a quality player come through the door, it gives them that excitement and you feel it around training. It gives everybody a lift.
"We've played against him for the last three years and know the quality he has got."
Giggs also believes the player himself will benefit from the move as he looks to play on a regular basis ahead of this summer's World Cup in Brazil.
"Coming here will help him with regards to playing for Spain if he is playing week in and week out (for United)," Giggs said.
I'm going to nail my colours to the mast and say I think he's much more likely to be yet another expensive square peg in United's round hole. Undoubtedly a quality player, but Veron and Berbatov were too. It's a shame and an expensive one too.- crivens