Wilshere, 21, believes the calibre of players now likely to be brought in by Arsenal shows they mean business on the pitch.
He added: "You look at the type of players like Higuain we are trying to bring in and you have got to be encouraged.
"I think we need a few more, not to step right into the team, but to add to the squad.
"We need our squad to be as deep as United's and (Manchester) City's. They can change their back four completely and still win. There is no way United would have won the Premier League trophy with 18 players."