THE sickening crunch that left Saints co-captain Luke Ball staggering to find his feet in round one continues to concern the club, with coach Ross Lyon saying the 22-year-old is unlikely to play this weekend.

Despite training solidly for the past two weeks, Ball was scheduled to have another scan yesterday amid fears for his health if he received another heavy blow to his head.

Ball was concussed and required stitches in his forehead after colliding heavily with Melbourne defender Matthew Whelan in the opening quarter of the season and he has not played since.

After missing round two against the Brisbane Lions, he was again sidelined in round three after his parents told the club he displayed lingering effects from the initial collision.

The subsequent tests showed he needed more time to recover.

Lyon said yesterday that "functionally, he's perfect, but there's still an element of risk (and) until that disappears, he won't play".

Sports injury specialist Dr Peter Brukner said resting Ball for another week was not unusual if he still had headaches from the concussion.

"One or two players a year miss two or maybe three weeks (through) concussion," Brukner said.

"This (Lyon's comments) tells us he still has symptoms, such as headaches, dizziness, feeling lethargic or he's not concentrating too well.

"These symptoms usually resolve in a matter of days but occasionally do persist and you can certainly get ongoing headaches."

Brukner said it was normal for a club to tread cautiously if a player still had headaches more than a week after concussion.

"Concussion is a fully reversible dysfunction of the brain … it will come good and he'll make a full recovery. It might just take a little longer than usual," he said.

Against Sydney last year, Ball was slightly concussed, and cut his mouth in a collision with teammate Matt Maguire. Unfortunately, the sight of the classy midfielder with his head bandaged has become all too frequent since he made his debut in 2003 and he joins a growing list of injured players, including Max Hudghton (thigh), Matt McGuire (foot) and ruckman Matthew Clarke, a late withdrawal last weekend with a hamstring strain, who Lyon said was doubtful again this week.

■ Carlton midfielder Nick Stevens had further tests yesterday to determine the cause of his neck soreness — a continuing problem that forced him to miss the final two matches last season.

The 27-year-old has played all three games this season but had precautionary scans on Sunday before joining Monday's training session.

The Blues said last night that the results of the latest scan would be available today.

■ Richmond forward Nathan Brown again will be on the sidelines when the Tigers meet his former club, the Western Bulldogs, in what looms as a crucial game for both clubs at the MCG on Friday night.

Brown had a stress reaction in the leg he broke in 2005 and has not played since the pre-season competition finished.

Coach Terry Wallace yesterday ruled him out of returning this week. "He's probably still at least a week away," Wallace said. "It's been four weeks now and we said it was probably a four-week injury … we're not taking any risks."

■ Collingwood's Alan Didak, last year's best-and-fairest winner, could return against Port Adelaide on Saturday at the MCG after overcoming knee surgery in the off-season.

Magpies football manager Geoff Walsh said Didak was "some chance" to play his first game for the year this week against the Power, but may return through VFL affiliate Williamstown.

"We've still got the main training session (today) to get through, but he's a chance either way," Walsh said.

With AAP