This one's not done yet after a thrills and spills Sportsground night.
The Connacht crowd in the sell-out 8,126 crowd fervently hoped that their underdogs could stay in this round of 16 two-legged tie by the end of the 80 minutes in Galway.
And they are still in it. For sure, Leinster are still favourites to progress to the quarter-finals at the Aviva Stadium next Friday on the back of a two-point victory last night.
But for the green-clad faithful in the Clan terrace and around the ramshackle ground, there was nothing but pride in the performance of Andy Friend's men as Connacht distinguished themselves in their first-ever appearance in the knock-out stages.
Johnny Sexton took a bit of a hammering as Connacht came forward whenever they could, starting both halves in a blistering fashion and showing they were not in awe of the world-class weaponry at Leo Cullen's disposal.
The Blues did show that quality at times, with James Lowe and Hugo Keenan linking to devastating effect - Lowe helped himself to two tries, Keenan to one.
But Jamison Gibson-Park's yellow card for the visitors opened the door for Leva Fifita's 61st minute try and that converted score ensures that there's still all to play for in Dublin 4.
In the end, Ross Byrne's penalty pushed Leinster's advantage out to five points ahead of the second leg, but Connacht will take massive encouragement from their performance.
Connacht rocked the visitors early on with incisive carries by Tom Farrell and Bundee Aki and, after James Lowe's attempted clearance was blocked by Fifita, his team-mate Porch raced onto Jack Carty's perfectly-timed pass to score.
Carty missed the conversion but Leinster's hopes of a swift response were frustrated.
Aki was prominent as Connacht pushed forward again and with Mack Hansen joining the party, the westerners continued to threaten.
Inevitably, the visitors built their way back into it. Sexton reduced the deficit with a 20th minute penalty and before Lowe scored unopposed after a superb move from inside the own half.
Ringrose got his side moving with a charge down the left and although Finlay Bealham momentarily stopped Leinster's momentum in midfield, Connacht didn't get enough men moving to cover on the right and Keenan's inside pass to Lowe put him into clear space.
Sexton's easy conversion made it 10-5 in his side's favour and it got even better for Cullen's side in the 27th minute, when again Connacht were far too passive in defence as Leinster cruised through the phases.
Lowe's pass released Keenan and the full-back repaid the compliment by assisting the Kiwi's second try, though Sexton failed to land the extras.
Connacht had to find something and a piece of Hansen magic almost provided, when he burned O'Brien on the outside and chipped Ross Molony before releasing Tiernan O'Halloran, but Josh van der Flier put him in touch.
Carty and Sexton traded penalties before the Connacht no 10 made it 18-11 with the last kick of the first half.
Again, it was the hosts who were straight onto the attack and Conor Oliver's break allowed Aki to go close to scoring. Leinster were penalised for offside and Carty reduced the deficit to four.
Not for the first time, the westerners messed up the restart as Farrell's kick was blocked by O'Brien and, off the ensuing five metre scrum, Lowe thought he scored his third try.
A knock-on scuppered that belief but the visitors cranked up the pressure through a series of scrums and eventually Jamison Gibson-Park sent Keenan over, though Sexton again missed the conversion.
If Connacht needed further encouragement, it came in the 57th minute when Gibson-Park was sin-binned for a high challenge on Kieran Marmion.
It took the hosts four minutes to score their second try against the 14 men, with Fifita diving over after Connacht mauled their way to the Leinster line and Carty made it a two-point game.
Then Connacht almost took the lead with 15 minutes remaining when replacement lock Oisin Dowling was just short as he attempted to dot down.
It would have been the perfect finish to a searing counter by Porch and Conor Fitzgerald off turnover ball.
With three minutes remaining, Byrne's three-pointer finished the scoring though not, crucially, the tie. Not yet.
CONNACHT: T O’Halloran (C Fitzgerald 41); J Porch, T Farrell (S Arnold 77), B Aki, M Hansen; J Carty, K Marmion (C Blade 61); M Burke (T Tuimauga 57), D Heffernan (D Tierney-Martin 61), F Bealham (J Aungier 70); G Thornbury (O Dowling 52), L Fifita; C Prendergast, C Oliver, J Butler (A Papali’i 61).
LEINSTER: H Keenan; J O’Brien, G Ringrose, R Henshaw (C Frawley 74), J Lowe; J Sexton (capt) (R Byrne 68), L McGrath (J Gibson-Park 51); C Healy (E Byrne 51), D Sheehan (J Tracy 62), T Furlong (M Ala’alatoa 62); R Molony, J Murphy (D Toner 70); C Doris (M Deegan 77), J van der Flier, J Conan.
Referee: Karl Dickson (England)
