Key All Blacks flanker Richie McCaw is confident of lining up in the first rugby Test against the Lions despite sending injury alarm bells ringing through the camp.

McCaw admitted he was battling an ongoing back strain ahead of the long-awaited first Test, which led to Waikato tearaway Marty Holah being whistled in from Brisbane as cover.

Coach Graham Henry insisted it was precautionary and that McCaw was still on track to wear the No.7 jersey at Jade Stadium.

"We're not panicking here, just being sensible," Henry said.

"Marty's here just to cover. It's a long shot but we've got to make sure we've covered all the angles."

Holah, a surprise omission from the first Test squad after his heroics for New Zealand Maori against the Lions, was to play for the Junior All Blacks against Queensland in Brisbane on Wednesday night.

Instead he was scheduled to fly into Christchurch about 9pm.

Henry said Holah wouldn't come into the reserves and would only take the field as a straight swap for McCaw if he were ruled out.

McCaw was unsure what brought on the latest back problem, but said he felt it after long periods of inactivity, such as plane flights, rather than when he was training.

It could even be brought on by "tying my shoelace".

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