After months of speculation, United has reportedly made a breakthrough in their pursuit of the 28-year-old Croatia international, with Jose Mourinho's men on the verge of a $A67 million deal.
Former United winger and assistant Giggs feels Perisic's imminent transfer will bring out the best in Marcus Rashford, Henrikh Mkhitaryan and Anthony Martial.
"It can be a boost for all the players," Giggs said.
"It not only excites the fans but also the players, when a new player comes in.
"If he comes, then the likes of Marcus Rashford, Henrikh Mkhitaryan and Anthony Martial have to step it up."
United has already invested heavily in the transfer market, spending $A126 million to lure Romelu Lukaku to Manchester.
Lukaku, who scored 25 Premier League goals for Everton last season as he finished second behind Golden Boot winner Harry Kane, made his debut in United's 5-2 pre-season win over LA Galaxy.
While Lukaku scored 53 Premier League goals in total for Everton, Giggs warned the Belgium international striker that he must adapt to increased pressure at United.
"The pressure will be on you. So he needs to develop a thick skin, he needs to listen to the coaches, because that's all that counts really," Giggs said.
"And if he misses a chance, the next one that comes along he needs to put it away because, as a centre-forward at United, you're under scrutiny all the time. I think he will score goals, but you need goals from all over the park.
"I've seen a bit of [Alvaro] Morata. I've seen more of Lukaku. The pluses with Lukaku are obviously that he's played in the Premier League and Jose has worked with him before, and he's got friends. He's friends with Paul Pogba, and that makes the transition that bit easier."