The Crusaders took control of the New Zealand conference after they beat the Blues 23-16 in a Super Rugby match in Timaru.
The result moves the Crusaders above the Blues for the first time this season and they must now beat the Hurricanes next week to hold on to that lead.
The loss was the Blues fourth in a row and puts their participation in the play offs in doubt after they had led the standings earlier in the season. The Blues did however pick up a losing bonus point which could be crucial.
Zac Guildford scored two of the Crusaders three tries and the Blues scored two but lost try scorer Rene Ranger after the first quarter of the match with a hamstring injury.
It was sweet revenge for the itinerant Crusaders, rendered homeless by the devastating Christchurch earthquake in February, who were beaten by the Blues 22-24 in the first round.
In their top-of-the-table rematch, which also served as a de facto All Blacks trial, the Crusaders held a decisive edge in the forwards, allowing left wing Guildford to cash in twice.
The Crusaders outscored the Blues three tries to two as their dogged defence held firm for long periods in the second half and captain Kieran Read said it showed the seven-times Super champions were peaking at the right time.
"It took an 80-minute performance and I'm really proud of the lads for getting over the line, " said Read,
"I think in that second half we really ground it out and that's a trade mark of what you need to do at this time of the year. "
But there was nothing to celebrate for Blues skipper Keven Mealamu as his side suffered their fourth consecutive loss and slipped to second in the New Zealand conference and fourth overall.
"When you make little lapses against a team like this they'll put points on you. We talked about it during the week and it's disappointing to lose. "
In the must-win match for both sides, the Crusaders were outplayed over the first 15 minutes, as they struggled to come to grips with the frantic pace in their first game after a bye.
Sonny Bill Williams conceded early points when he gifted Luke McAlister an easy penalty by not releasing the ball when the Crusaders were under pressure.
Rene Ranger then increased the lead after fullback Jared Payne created the extra man in the backline giving the left wing room to chip ahead and win the race for the ball.
But from 0-8 down the Crusaders went 10-8 ahead in the space of two minutes starting with a penalty by Dan Carter then a try to Matt Todd which started when Andy Ellis stole the ball from the back of an Auckland scrum on halfway.
Carter and McAlister exchanged further penalties and the Crusaders, denied a second try when Read was ruled to have obstructed the defence, led 13-11 at halftime. Crusaders centre Williams suffered a hip injury in the 22nd minute to be replaced by Ryan Crotty and the Blues lost Ranger four minutes later to an ankle twinge with Lachie Munro replacing him.
Read made amends from the kick off in the second half when he swooped on the ball behind a Blues ruck and sent Guildford over in the corner for his first try.
Blues' prop Charlie Faumuina, the sole non-All Black in the front rows, bullocked his way over in reply but McAlister blew the change to level the scores when his conversion attempt went wide.
As fatigue began to set in, the error level rose and both sides wasted scoring opportunities before a precision cross-kick from Carter five minutes from time saw Guildford score his second try.
In the final round-robin matches next week the Crusaders play the Hurricanes and the Blues play the Highlanders.
Final Score Crusaders 23 Blues 16
Tries - M Todd, Z Guildford 2
Pen - D Carter 2
Con - D Carter
Tries - R Ranger, C. Faumuina
Pen - L McAlister 2
Referee: Craig Joubert
Assistant referees: Vinny Munro, Kane McBride
Television match official: Keith Brown
Crusaders :1. Ben Franks , 2. Corey Flynn , 3. Owen Franks , 4. Brad Thorn , 5. Sam Whitelock , 6. George Whitelock , 7. Matt Todd , 8. Kieran Read (c) , 9. Andy Ellis , 10. Dan Carter , 11. Zac Guildford , 12. Sonny Bill Williams , 13. Robbie Fruean , 14. Brent 4Ward , 15. Tom Marshall
16. Quentin MacDonald , 17. Wyatt Crockett , 18. Luke Romano , 19. Jonathan Poff , 20. Willi Heinz , 21. Matt Berquist , 22. Ryan Crotty
Blues: Jared Payne, Joe Rokocoko, Benson Stanley, Luke McAlister, Rene Ranger, Stephen Brett, Alby Mathewson, Peter Saili, Luke Braid, Jerome Kaino, Ali Williams, Anthony Boric, Charlie Faumuina, Keven Mealamu (capt), John Afoa.
Reserves: Tom McCartney, Tevita Mailau, Chris Lowery, Sean Polwart, Chris Smylie, Lachie Munro, Sherwin Stowers.