LUKE Ball, the AFL's regular battering ram, will have more scans this week to monitor the bruising of his brain that was detected after his latest concussion.

St Kilda coach Ross Lyon said yesterday while he was hopeful Ball would return in round four, it was unclear how long the co-captain would be on the sidelines.

It was Ball's mother, Jenny, who prompted the Saints to further investigate the midfielder's condition after she noticed her 22-year-old son was sleeping excessively following his round-one collision with Melbourne's Matthew Whelan.

A neurologist and neurosurgeon advised St Kilda last Thursday week that Ball should not travel to Brisbane to play against the Lions in round two. Then, after a further MRI scan this week showed the swelling in his brain had reduced but not disappeared, the experts ruled him out of tonight's game against the Western Bulldogs.

Jenny Ball told The Age last night that the duration of her son's time on the sidelines depended on the results of the scans he has this week. But despite his propensity to come off second-best in head clashes, she said she and her husband Ray were certain that their child was being well managed.

"(St Kilda doctor) Ian Stone and the neurologist and Ross Lyon spoke to Luke at length and said, 'We're looking at your future'. He's busting out of his skin, but he's just got to be patient.

"We don't really know, but they think because it's there (the oedema), we're not going to take any chances … But if it's still there in six weeks' time, maybe they'll think it's just scarring and it's going to be there. But they don't expect that," Jenny Ball said. "Stoney and Ross Lyon have both totally reassured us that they would not at any stage risk him … so we are happy and totally confident that Luke is in their hands, and that when they say he's ready to play, he'll be ready to play, and it's their decision."

After spending considerable time off the field after his heavy opening-term clash at the MCG 15 days ago, Ball later returned to the field. His health deteriorated significantly the next afternoon.

Lyon couldn't say yesterday whether Ball's current condition was worse due to the cumulative effect of his many head-high clashes since making his debut in 2003.

"The fact is he could go down the race and play and get through, but there is a risk there that if he was to receive a full-on frontal knock to the head, which he received in round one, that would put Luke at risk," Lyon said.

"But it is something that in a week's time we're hoping will be perfect and then he'll play."

Ball has been training in a helmet ever since his injury and is expected to wear the head protection when he returns to senior football.

Meanwhile, Nick Riewoldt tonight will play his first match of the season after overcoming a hamstring complaint. He is being brought straight back into the seniors. "We need to manage him, the rest of the competition's had seven or eight games on him … he's not going to be able to play 100 per cent of the game," Lyon said.

There are queries over the fitness of the Saints' chief ruckman Matthew Clarke, who had a hamstring spasm at training during the week, but Lyon said yesterday he was "pretty confident" he would play. But he did bring big man Barry Brooks — the 15th pick of the 2001 draft, who has played only eight senior games — into the line-up this week.

Lyon said former West Coast ruckman/forward Michael Gardiner had had another setback after wearing new orthotics in a VFL game last weekend that irritated one of his feet, and is expected to play reserves again this week.