All Blacks captain Kieran Read has broken his thumb in the Crusaders' big win over the Cheetahs in Bloemfontein, an injury which requires surgery and which will put him in doubt for the British and Irish Lions series.

Read, who has only just returned from wrist surgery in the off season, left the field late in the first half of the match, and while the Crusaders carried on regardless, his injury could have big repercussions for the national team.

The first test against the Lions at Eden Park is on June 24 - eight weeks away. If the reports out of Bloemfontein are accurate, Read could struggle to make that match.

Fellow loose forward Jerome Kaino is already in doubt for the opening test due to knee surgery.

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Crusaders assistant coach Jason Ryan said it's "extremely disappointing for Kieran and the All Blacks".

"The guys has worked so hard off the field to get his hand right from the surgery he had during the offseason and has been world class since returning to the field," said Ryan.

"Obviously it's disappointing and will be concerning for the All Blacks."

Ryan says they have no idea what the time-frame would be for Kieran Read's return to rugby is and will "probably be determined once he's had his surgery".

The Crusaders, meanwhile, are rumbling on - their seven-try victory over the Cheetahs extending their lead at the top of the table in a performance which again showed their attacking ability.

Their back three of George Bridge, Seta Tamanivalu and David Havili were lethal, with left wing Bridge repeating his feat of last weekend against the Stormers by scoring a hat-trick, and fullback Havili scoring a double.

The Cheetahs, dangerous as usual on the counter-attack, were constantly on high alert against the trio, who were allowed to run free due to the work of the Crusaders' pack and excellent navigational skills of first-five Richie Mo'unga.

"They were very clinical, they finished every opportunity," Cheetahs skipper Francois Venter said afterwards.

Asked why the Crusaders were so dangerous in possession, he said it was due to "their presence in contact and they move the ball the whole time. Just when you think you've got them they move the ball again.

"They had numbers in the wide channels and with their ability to offload they put us under a lot of pressure."

The bonus point win, which allowed Scott Robertson's men to go four points above the Chiefs, was not without its issues for the visitors, however.

Apart from the injury to Read, Crusaders captain Sam Whitelock was sinbinned for the final 10 minutes of the match due to a retaliatory elbow to the face of Cheetahs prop Charles Marais.

Whitelock struck out in frustration after being tackled in the air and, while it only grazed Marais, it was a piece of ill-discipline which should disappoint the lock.

Mitch Hunt, who replaced Mo'unga for the final quarter, soon joined Whitelock in the bin for a ruck offence, meaning the Crusaders played the final three minutes with 13 players.

The almost constant blast of referee Frederico Anselmi's whistle was a strange way for what was until that point a free-flowing match to end.

The Cheetahs, with only two wins this season and marked for a cull under Sanzaar's re-shuffle of the competition, were well in the game in the first half, responding straight away to Bridge's first try, and they were unlucky to see Sergeal Petersen's try ruled out due to a forward pass.

In what was a double blow for them, straight away Mo'unga took advantage with a perfect kick-pass to Bridge on his own on the left touchline, and the quick No11 went on an angled 50-metre run to score under the posts.

The converted try gave the Crusaders a 22-7 lead at halftime and they put the home side to the sword after the break, their eagerness to support and superior ability to put players in space meaning the Cheetahs were constantly scrambling.

When the home side did win possession, their fatigue was plain to see, although they did take advantage of their numerical superiority to score what was a deserved try to wing Petersen to finish the match.

Crusaders 48 (David Havili 2, George Bridge 3, Richie Mo'unga, Mitchell Drummond tries; Mo'unga pen; 5 cons)

Cheetahs 21 (Raymond Rhule, Ox Nche, Sergeal Petersen tries; Niel Marais 3 cons)

Halftime: 22-7

Click on the match page links below to see full match stats: