Massimo Ambrosini has welcomed Alberto Aquilani to Milan, but warned that nobody can substitute Andrea Pirlo.
The latter left the Rossoneri over the summer to join Juventus, the same club who opted against signing Aquilani outright following his loan spell.
However, the midfielder is now on his way to San Siro after an agreement was reached with Liverpool.
"Pirlo can't be replaced in terms of his character and personality, but it is unjust to make comparisons," Ambrosini told La Gazzetta dello Sport.
"Andrea marked an era here, but whoever replaces him can do well by interpreting the role in a slightly different way.
"Aquilani will be useful because he has different characteristics to the midfielders who are already at the club.
"He played with consistency and recovered his fitness at Juventus. I don't see a reason why he wouldn't do well here."
The former Roma youth product is expected to officially complete his move to Milan at some stage on Thursday.