An imposing block of four matches against massive South African packs is likely to see Queensland skipper James Horwill put in cotton wool for Friday night's Super Rugby clash with the Melbourne Rebels.

Horwill (ankle) and fellow tall timber Van Humphries (thumb) remain hopeful of overcoming injuries to turn out for the Reds at Suncorp Stadium but coach Ewen McKenzie is reluctant to risk the duo.

McKenzie will decide on Tuesday whether to rush them straight back into action against the Rebels or hold them back for the four consecutive contests against beefed-up South African opponents.

The Reds meet the winless Cheetahs in Brisbane on Saturday week before flying out to the Republic the next morning to play the Lions and Stormers, and then returning home for a searching test against the defending champion Bulls.

"It's a tricky timetable with a trip to South Africa basically only being the week after (the Rebels match) so we need to make sure people play when they are 100 per cent," McKenzie said.

"What we can't afford to do is have any relapses because they then become a three-week injury instead of one."

Wallabies lock Horwill, who started the season at blind-side flanker, missed the Reds' 31-25 victory over the Brumbies in round three when Humphries suffered his cracked thumb.

The injuries creates an opportunity for Adam Wallace-Harrison to start his first Super Rugby match back after three seasons in Japan while another former Brumby, Radike Samo, is also fit to return after recovering from a pre-season finger injury.

Helped by a timely bye, Horwill and Humphries, wearing a guard, trained on Monday at Ballymore despite their problems but the captain conceded there were doubts whether painful bone bruising would allow him to play to capacity.

"Whether it's this weekend or not it's a little bit up in the air but more than likely I'll definitely be right for the week after if not this week," he said.

"After the Rebelswe've got four South African teams in a row.

"They're pretty important games in the scheme of things and they're performing well ... so they're going to be tough games for us.

"They are going to be physical and ask a lot of you so we need to make sure we have guys who are fit to go. You don't want to be carrying too many people there."

The injury-hit Rebels, who gained extra credibility with a 34-32 loss to the Sharks last Friday, also have their problems in the lineout with New Zealand locks Kevin O'Neill and Hoani McDonald on the sidelines.

But the biggest blow for the fledgling franchise is the four-week loss of fullback Mark Gerrard who has been the most influential Melbourne player since missing the opening round thumping by NSW.

Former rugby league international Luke Rooney looms as Gerrard's logical replacement with utility back Julian Huxley, playing inside centre, combining nicely with playmaker Danny Cipriani.

Brought to you by AAP © 2024 AAP