Sam Whitelock in doubt for All Blacks after playing Super Rugby final with broken thumb

Sam Whitelock of the Crusaders. Photo / Photosport.co.nz

The All Blacks could be light on locks for the start of the Ireland series, with Sam Whitelock in doubt through a broken thumb.

Whitelock provided the Crusaders with a pre-match boost ahead of Saturday night's Super Rugby Pacific final after seemingly overcoming the thumb injury that saw him miss his side's semifinal win over the Chiefs the previous weekend.

But following the Crusaders' clinical victory over the Blues at Eden Park - a triumph to which he greatly contributed - coach Scott Robertson confirmed Whitelock had played the match with a broken thumb.

"He's got an incredible capacity to play through pain…to play with a broken thumb," Robertson said after the champions had arrived back to a hero's welcome in Christchurch.

"Last week he definitely wasn't right because he never says he's not right and he sort of hesitated.

"This week he was so on. He was a commander-general. He worked so well with Scooter (Scott Barrett). The performance was a throwback to his best."

Whitelock indeed played a crucial role in the victory, making eight tackles, winning two turnovers and causing havoc at lineout time, ensuring the Blues lost more lineouts (10) than they won (nine) while helping the Crusaders' complete a perfect 11-from-11 record.

Sam Whitelock of the Crusaders during a lineout in the Super Rugby Pacific final. Photo / Getty

But the 33-year-old is now facing a race against time to be fit for the first test in a three-match series against Ireland, starting at Eden Park on July 2.

Whitelock's injury could cause a rethink for All Blacks coach Ian Foster and his selectors after fellow lock Josh Lord last week suffered a ACL rupture, squashing his hopes of adding to the two caps he won last year.

The All Blacks initially named five locks in their 36-man squad for the series, with Whitelock and Lord joined by Crusaders skipper Barrett and Chiefs pair Brodie Retallick and Tupou Vaa'i.

After an MRI scan revealed the extent of Lord's knee injury on Friday, ruling the 21-year-old out for the international season, the All Blacks opted against bringing in a replacement player.

But whether Whitelock will continue to play through pain or whether he is instead facing a spell on the sidelines, the All Blacks will be wary of being understrength in the set piece against the Irish.

The first test in Auckland will be followed by matches at Forsyth Barr Stadium in Dunedin and Sky Stadium in Wellington.