He said: "Michael is an exceptionally good player but I just question the injury scenario. If he picked up the injuries he did at Newcastle, I couldn't afford that. I couldn't afford to be without him for long spells. That's the doubt I would have.
"I need a striker that's going to be available for 30 games next season - that's the key.
"Finding a good striker is the first thing but also one who is going to be available on a regular basis.
"That's not happened for Michael over the last four years at Newcastle. For me at this time, it's not something I'd be interested in."