United are currently second in the Premier League but are without midfielders Tom Cleverley and Anderson due to injury, while Darren Fletcher is taking an indefinite break from football for health reasons.
United have also been hit with the injury to defender Nemanja Vidic, who is out for the rest of the season.
Ince spent six years at Old Trafford, winning two Premier League titles before moving to Inter in 1995, and the former Blackburn Rovers manager believes Sir Alex Ferguson needs to spend in January if United are to compete with Manchester City at the top of the league.
Ince told BBC Radio Five Live: "I feel they need that creativity in midfield, losing Paul Scholes was a big loss obviously.
"You're not going to get players like Roy Keane or Bryan Robson, those players aren't around anymore.
"The game has changed since then and you don't get those type of characters, so he [Sir Alex] has got to look at another way of controlling the midfield and I think that can come from creativity in someone like Luka Modric or Andres Iniesta, they are the players I would be looking at.
"I'm sure Sir Alex will take stock and he'll be looking at what type of player he will need in January and it won't just be in midfield, I'm sure he's looking at a centre-half with Vidic being out.
"But I'm sure he knows what to do, there's no point me telling him what to do because he's the greatest manager I've ever played under."
Also injured are Javier Hernandez, who is out until the new year, as well as fellow strikers Dimitar Berbatov and Michael Owen.
According to Ince, the lack of firepower needs to be addressed by Sir Alex, with a new goalscorer to be brought in to take the pressure off Wayne Rooney, who scored his first Premier League goals in nine matches with a brace against Wolves last weekend.
He said: "There is a lot of pressure on Rooney and we saw what that did to him in the World Cup.
"If you are going to compete with the likes of Manchester City and Chelsea you need someone who is going to score you 20 goals a season and you can't just rely on Wayne Rooney to do it year in and year out.
"Nani has chipped in and Ashley Young was flying early on, but they have quietened down form-wise, so you wonder where the goals are going to come from.
"Berbatov's not playing enough, Michael Owen is out injured again and Danny Welbeck is still a young lad but he will chip in with goals."
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