All Blacks loose forward depth faces another test, after Liam Squire broke his thumb during the southerners' Super Rugby thriller against the Cheetahs in Bloemfontein.

With national team skipper Kieran Read already sidelined with the same injury and veteran blindside Jerome Kaino undergoing recent knee surgery, Squire loomed as an important cog in the loose forward mix against the British & Irish Lions next month.

But 10 minutes into this morning's encounter - a 45-41 come-from-behind win for the Highlanders - he needed strapping on a swollen thumb and was forced from the field 10 minutes later, replaced by Gareth Evans.

Afterwards, coach Tony Brown confirmed the worst fears.

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"It is broken and he's on the plane home," said Brown. "He's probably looking at six weeks out for a broken thumb.

"With Kieran Read out, Liam was probably next cab off the rank [for the All Blacks]. Hopefully, both Kieran and Jerome Kaino can get in time for the Lions.

"He's a massive loss for us."

Highlanders centre Malakai Fekitoa also sent a scare through the Highlanders and All Blacks ranks, when he left for a concussion test midway through the first half, but he later returned to the fray.