Second-half replacement Mark Van Gisbergen landed the dramatic conversion deep into injury time to snatch victory for Wasps and keep their Guinness Premiership championship hopes alive.

Wasps looked down and out when they trailed 26-13 to fourth-placed Saracens with 10 minutes remaining.

But Irish scrum-half Eoin Reddan, scorer of two tries in last weekend's epic Heineken Cup victory over Leinster, grabbed two more in a do-or-die finish.

Van Gisbergen came off the bench to convert both, the second from the left-hand touchline three minutes into injury time.

Saracens, who did most of the first-half defending, grabbed the initiative with a classic try in the third minute of injury time in the first half.

Fly-half Glen Jackson launched a kick from his own 22 which was collected by Fijian speed merchant Kameli Ratuvou, who ran deep into Wasps territory from the halfway line.

Ratuvou, tackled by England winger Josh Lewsey, passed inside to French full-back Thomas Castaignede who was left with a clear run to the line.

Jackson's conversion put Saracens, who had trailed 6-0 after 17 minutes, 13-6 ahead at the interval.

Saracens flanker David Seymour halted Wasps' most dangerous first-half move with a tackle on centre Fraser Waters and Jackson put Saracens level with penalties.

The visitors increased their lead with Jackson's third penalty in the 48th minute.

They looked home and dry two minutes later when Castaignede drove at the Wasps backline to set up Sarries' second try, with Dan Scarbrough providing the pass for heavyweight Samoan prop Cencus Johnston to force his way over and stretch their advantage to 21-6.

But Wasps refused to concede defeat.

They stormed back, with Lewsey being halted a foot short of the line by Saracens skipper Simon Raiwalui before the home side scored their first try in the 56th minute.

Reddan and centre Dominic Waldouck combined to move the ball right for full back Danny Cipriani to squeeze over in the corner, with Walder landing the conversion from the touchline.

But the fightback looked short-lived as Saracens responded with their third try four minutes later as Jackson sent centre Rod Penney over as they had men spare on the right.

Van Gisbergen was introduced in the 69th minute and 60 seconds later landed his first conversion after an immense drive by flanker James Haskell provided the opening for Reddan to run in Wasps' second try.

The home side hurled everything into attack and, just as it looked as though their efforts were in vain, Reddan snatched the ball from the base of a scrum and burst down the blindside for a last-gasp opportunist try which gave Van Gisbergen chance to land the winning kick.

Saracens, with a losing bonus point, are still two points ahead of Wasps but the battle for top four places looks set to go right down to the wire.