Ighalo, signed on loan from Shanghai Shenhua until the end of the season, will join up with the United squad this weekend, ahead of Monday's Premier League trip to Chelsea.
“I don't think he's a signing for the long term," said Scholes. “I think his scoring record in China is very good, but is it that credible? I don't know.
“He's an out-and-out centre forward and I don't think United have an out-and-out centre forward. He'll play with his back to goal and he might bring players into play.
“It's good to have an extra body, but when you're United, you want an extra body with quality, and he's got that to prove.
“He'll bring something different. I don't see him starting many games."