FRUSTRATED Brisbane Lions coach Leigh Matthews admits he is no closer to determining when injury-plagued veteran Nigel Lappin will return to the AFL.

While Lappin is officially suffering from a corked thigh, Matthews said the jury was out on what exactly was troubling his triple premiership midfielder.

Lappin trained strongly last week and looked set to return against the Kangaroos on the Gold Coast last Saturday night but was pulled at the last minute.

The 30-year-old sustained the corked thigh in the first round win against Hawthorn, adding to his woeful recent luck.

Lappin missed the entire 2006 season due to ankle surgery and was troubled by an elbow injury in the 2007 pre-season before making an impressive comeback against Hawthorn.

Adding to Matthews' frustration is the fact no one on the Lions' medical staff can tell him exactly what is Lappin's problem.

"The bruising on the thigh that has troubled him has largely settled down, but the other part of the muscle seems to be sore and tight," Matthews said.

"It's difficult to diagnose exactly what his problem is. Is it just tightness which needs a few days or has he strained muscle fibres?

"At the moment I am a bit in the dark in terms of what to expect."

Matthews said he hoped to learn more about Lappin's injury this week.

"He trained normally on Wednesday, but when he ran around on Friday he wasn't quite okay," he said.

"We have to accurately diagnose it. At the moment we need a firm diagnosis - that's something we have to determine today.

"He's missed a fair amount of football now.

"It's very frustrating because he's a good player, but very frustrating for Nige because he has only got on the field (and got injured again)."

Matthews said the latest setback was just another "freaky" addition to Lappin's injury history.

"He got a bad knock in that leg in the practice game he played 10 days before round one and then he got another knock in the same leg, so it's a bit freaky really," he said.

"But Nigel has been suffering from those freaky things.

"He got an ankle injury that kept him out of the whole year - that doesn't happen that often either.

"At the moment getting his body consistently right has been a challenge that he and we haven't been able to solve at this point."

Matthews said he had spoken to AFL operations manager Adrian Anderson about why Hawk Luke Hodge was not called to answer for the attempted trip on Lappin in the round one clash that did the damage.

"But it's come and gone. I made an observation and left it behind," he said.

Meanwhile, Matthews said another injury-prone player - Josh Drummond - was in the "selection mix" for the Lions' round five Telstra Dome showdown with Carlton on Saturday night.

Drummond has been eased through reserves team Suncoast Lions this season after overcoming shoulder, hamstring and elbow injuries.