IAN Holloway will watch video footage of Matthew Briggs' best and worst career performances before deciding whether to offer the trialist a deal.
Left back Briggs has featured in two pre-season friendlies – against Dartford and Stevenage – since linking up with the Lions at the start of last week.
But Holloway admits he has not yet decided whether to sign the 23-year-old.
The Millwall boss cannot understand why the former England U21 international has so far failed to deliver on his undoubted potential – and is looking for answers.
"Briggs is growing on me but I still need to find out one or two bits about him because I only enter into relationships that I'm sure about," Holloway said.
"When people try to change a relationship, I don't like it because I'd never do that myself.
"I have got to make sure Briggs wants the same things as I do and that I can help him with whatever has stopped him from getting those things.
"If I bring someone to my club who might not start well and then cannot handle it, then I'm wasting my chairman's money.
"I need to find out certain things because I cannot understand for the life of me, with his athleticism and his wonderful left foot, why Fulham dreamt of letting him go.
"At one stage he was in the England set-up so maybe now he doesn't feel wanted or loved, but I can't bring in people who can't deal with that and who don't fight back.
"I really like Scott Malone, so I've got to bring in someone who can push him and challenge him – but I don't care who plays.
"I haven't watched Briggs as much as I should have done so we're going to watch some of his games – one good one and one scheisse-pants one that is his worst fear.
"I want to see why things haven't worked out. I think he stands there in a game wondering if he's playing well or not and you can't let those thoughts in.
"Can I cure that? I won't do anything if I can't, but if I can we could have one hell of a player on our hands."