Blues backrower Peter Saili scored a try in extra time to hand his team a 40-36 victory over the Waratahs in their second Super Rugby pre-season trial match in Whangarei, New Zealand.
Led by captain Brendan McKibbin, the Waratahs scored six tries in all, including a second-half hat-trick from 21-year-old winger Tom Kingston.
Although they held a slim advantage going into the final minutes, a last minute charge saw Saili bash his way over from close range to clinch the win after the siren had sounded.
"A few blokes played well today," head coach Michael Cheika told reporters after the game.
"Kingston played well, Israel Folau had another good game and got a lot of touches.
"I have been training them really hard so there is bound to be a bit of flow on. Considering what we've put into them, I was pretty happy with the condition they came out on to the field in.
"What I don't like is losing, we should have won. But this was a good sign and we've still got seven or eight international players back home."
McKibbin's side had the Blues stretched early on as they found space out wide, but it was the home side who struck first through young winger Lolagi Visinia.
Fullback Albert Nikoro's conversion gave the Blues a 7-0 lead after 12 minutes, but the visitors hit back just before the end of the first quarter.
In his first game in NSW colours, Wallabies flanker Michael Hooper put in a strong performance and it was his turnover on the Blues' five metre line that led to fullback Cam Crawford scoring for the visitors, his second try in as many appearances.
A Blues' try from a lineout gave them a 12-7 lead at halftime but a second-half revival saw the Waratahs roar back into the match after the break.
When a grubber kick from Blues' centre Malakai Fekitoa's backfired, young NSW newcomer Jed Holloway latched onto it and ran 40 metres to score, levelling the scoreboard at 12-all.
Folau's introduction to the game at halftime had an immediate impact as he found plenty of holes in the Blues' defence and set up flyer Kingston for a brace of tries, giving the visitors a two-score advantage.
The Blues managed to narrow the deficit through prop Tim Perry but some more slick footwork by Folau saw him carve up the defence to score a brilliant individual try to add to his two assists, only for wing Waisake Naholo to bag his second score of the afternoon, straight from the ensuing re-start.
With the Blues ahead 33-31 with 11 minutes remaining, Kingston's third try of the afternoon appeared to have clinched the victory for the visitors with just minutes left on the clock.
But Saili's try at the death following a sustained passage of play snatched it for the Blues as the 5,000 strong Northland crowd erupted into applause.
Final Score Blues 40 (12) Waratahs 36 (7)
Tries : Peter Saili 2, Waisake Naholo 2, Lolagi Visinia, Tim Perry
Con : Albert Nikoro ,Baden Kerr 4
Tries : Tom Kingston 3, Cam Crawford, Jed Holloway, Israel Folau
Con : Brendan McKibbin ,Bernard Foley , Matt Lucas
15. Albert Nikoro,14. George Moala,13. Rene Ranger,12. Francis Saili,11. Lolagi Visinia,10. Chris Noakes,9. Bryn Hall,8. Peter Saili,7. Luke Braid,6. Steven Luatua,5. Ali Williams (C),4. Liaki Moli,3. Angus Ta'avao,2. Quentin MacDonald,1. Tom McCartney
Reserves: James Parsons, Tim Perry, Culum Retallick, Brendon O'Connor, Charlie Faumuina, Ronald Raaymakers, Kane Barrett, Jamison Gibson-Park, Malakai Fekitoa, Marty McKenzie, Baden Kerr, Waisake Naholo, Frank Halai
Michael Alaalatoa (Southern Districts)*, Richard Aho (Randwick)*, Kotoni Ale (Manly)*, Tom Carter , Cam Crawford, Kane Douglas, Israel Folau , Bernard Foley (vice captain), Michael Hodge, Jed Holloway, Luke Holmes,Michael Hooper, Rob Horne , AJ Gilbert (Northern Suburbs)*, Tom Kingston , Matt Lucas, Brendan McKibbin (captain) ,Tolu Latu (Sydney University)*, Dane Maraki (Manly)*, Drew Mitchell, Elijah Niko (Eastern Suburbs)* , Greg Peterson , Paddy Ryan, Jeremy Tilse (vice captain), Lachie Turner, Peter Samu (Randwick)* , Will Skelton (Sydney University)*,John Ulugia,Ben Volavola
* Indicates non-contracted players