Todd Blackadder warned this test series window could have a big bearing on the Super Rugby competition and in a cruel twist it turns out his Crusaders side has been worst affected with one match still to play.

No8 Kieran Read was expected to miss Saturday's third test against Ireland in Hamilton with concussion after two head knocks in successive tests for the All Blacks but playmaker Dan Carter's dramatic withdrawal with a hamstring strain seriously compounds things for the Crusaders who had their campaign cut short after building a nice little run.

Concussion injuries affect people differently and there is no way of knowing when 26-year-old Read will return until tests show he is ready.

Similarly, hamstring injuries can be niggly affairs. Carter, 30, strained the same right hamstring when playing for the Crusaders at Twickenham last year and it took more than six weeks to come right, which included a false start. It was the first time he had injured a hamstring but, as he showed last year and on Tuesday, they are also easy to aggravate, something which could be an issue for the All Blacks in the Rugby Championship which starts in August.


As All Blacks coach Steve Hansen said: "He should be a couple of weeks or three weeks [out] - we're not really sure. It's not that bad but hamstrings are annoying things if you're ever fast enough to have one. They tend to hang around for a bit."

Earlier this season Blackadder called Read the best rugby player in the world. World record test points scorer Carter, who had battled through his groin injury and was nearing his best, can also lay claim to that title.

Both are essential to the Crusaders' hopes of winning their first title since 2008. Read's ball carrying, defence and re-start has few peers and Carter's sharpness and goalkicking was looking extremely encouraging. If nothing else, his penalty from 55m in the first test at Eden Park proved he was back.

After a slow start which coincided with Carter's absence, the Crusaders were building momentum and gaining slightly on the Chiefs with comprehensive 50-point victories over the Blues and Highlanders. The former left many still questioning their title credentials given the paucity of the opposition. The latter, against a motivated and effective team with plenty to play for under Jamie Joseph, left most in no doubt.

The Chiefs top the New Zealand conference and the overall Super Rugby table and their showdown with the Crusaders in Hamilton on July 6 will have a big bearing on the play-off positions. Both Read and Carter must be in doubt for that match.

The Chiefs are also the biggest beneficiaries of the two injuries within the All Blacks, with Sam Cane and Liam Messam starting thanks to a re-shuffle among the loose forwards and first-five Aaron Cruden replacing Carter.

With midfielder Sonny Bill Williams carrying his robust form into the test window, coach Dave Rennie will hope his charges come through the dead rubber at Waikato Stadium without any issues.

Elsewhere the Hurricanes have been hit hard by the season-ending injuries to loose forward Victor Vito, who injured a knee in the first test, and halfback TJ Perenara, who broke an ankle in a friendly match against the Reds. The Blues, their title hopes long gone, have added lock Ali Williams and wing David Raikuna to the long-term injury list. Lock Filo Paulo has also been banned for punching in the North v South match.

In Australia, Reds skipper James Horwill faces a long spell on the sidelines after having surgery on a badly torn hamstring.