Medical updates on Anton Oliver's recovery from a calf muscle tear and whether it dovetails with the All Blacks' first test against the Lions will dominate the leadup to that series.

Oliver is the fourth test forward now in doubt after earlier mishaps for Keith Robinson and Richie McCaw and a pending departure for Norm Maxwell.

Another injury scare surrounds incumbent test halfback Byron Kelleher after he limped out of the Chiefs' draw against the Brumbies with a groin injury.

Early forecasts rated Oliver's return in a four-to-six-week bracket, with the Lions series starting in Christchurch in a shade under seven weeks.

"I had Olo Brown with a massive tear of his calf muscle in 1997 and six weeks to the day, he played again," All Black doctor Graham Paterson said.

"That was as serious a calf tear as they come and he had no hiccups in his recovery, it all went perfectly well."

Oliver was due to have a scan on his damaged left leg today and there will be a similar assessment for Kelleher.

Chiefs coach Ian Foster admitted the initial prognosis looked poor for the combative halfback ahead of the Lions tour.

"He's pretty sore and limping pretty bad - it's not looking good," Foster said.

Meanwhile Paterson said Oliver's initial fears that he had suffered an Achilles tendon injury gave him some idea of how significant the injury was.

"It is all about estimates at this stage, it could be in the four-to-six- week vicinity for full activity, it could be that time before he is able to train fully."

The All Black hooker's injury and Kelleher's problem have claimed attention in the rundown to the final week of Super 12 qualifying.

The Waratahs, Crusaders and Hurricanes are through to the playoffs; the Bulls, Highlanders and Blues are chasing the last place.

Oliver had been an inspiring leader for the unfancied Highlanders this season and was expected to be a key part of the All Black pack against the Lions.

But his first-half exit during his side's 27-13 loss to the Crusaders and initial fears he had damaged his Achilles, tainted the Carisbook match.

All Black concerns were underlined when the Crusaders' Justin Marshall inquired about Oliver's health and reeled away in disbelief.

Marshall had suffered an Achilles tear in 1998 and understood the implications had Oliver's suspicions been correct. But after an examination it was decided Oliver had suffered a severe calf muscle pull.

"I thought it was my Achilles," said Oliver who had suffered that injury on his other leg in 2002.

"It sounded and felt exactly like it did when I snapped it. It went all numb and I couldn't move my foot."

Defeat for the Highlanders has left them in a scrap for the last semifinal berth, one the Bulls can seal by beating the Stormers this weekend.

The Blues must beat the series leader, the Waratahs, in Sydney and the Highlanders must overcome the Chiefs in Hamilton and hope the Bulls lose, if they are to have a tilt at the semifinal vacancy.