The striker left the Reds for Sheffield United last week.
"I'd like him to have stayed. I can see some of the reasons why, but if you were asking me whether to go with Brewster or Divock Origi, for me, it'd be Origi going.
"But on the football side, I can see he isn't playing as many games, so maybe it'll get him that first-team experience.
"There's not too many forwards that have the aggression that Brewster has though.
"There's a couple of others that could have gone, Xherdan Shaqiri for example could've brought a few quid in.
"Maybe the outgoings haven't gone the way they'd like – but the incomings have been really good."