The North-West outfit are under pressure to spend having only bought midfielder Marouane Fellaini for around £27m in the summer.
Widespread reports have claimed that the current Premier League champions are closing in on a £37m swoop for Mata.
"He would be a good signing for Manchester United," Bosnich told talkSPORT. "Manchester United are one of the biggest clubs in the world. They are to going to have to pay top dollar for a top player and this man is a top player."
United are currently seventh in the Premier League table.