|European Champions Cup|
|Ospreys (6) 15|
|Pens: Biggar 5|
|Saracens (9) 15|
|Pens: Farrell 5|
Dan Biggar's last-minute penalty kept Ospreys in Champions Cup quarter-final contention with a draw with Saracens.
The result leaves defending champions Saracens with their own precarious hopes still alive, but will likely need other results to go their way.
In a game of few try opportunities, Biggar and opposite number Owen Farrell produced a kicking masterclass.
The British and Irish Lions fly-halves both kicked all five of their penalty chances.
Clermont Auvergne had been the runaway Pool 2 leaders but suffered a surprise 34-21 defeat at previously winless Northampton earlier on Saturday.
That left the door slightly ajar for both Ospreys and Saracens, who knew a win at the Liberty Stadium would then give them the chance of topping the group in next week's final round of matches to secure an automatic quarter-final place.
Perhaps because of the raised stakes, the first half at the Liberty Stadium was a cagey affair, with the action taking place mostly at the breakdown and little threat to either side's try line.
Saracens' juggernaut forwards Billy Vunipola and Will Skelton were able to punch occasional holes in the home defence, but Ospreys held firm - although they did offer up three kickable penalties that Farrell turned into nine points.
Ospreys' biggest attacking threat was undoubtedly at half-back, with British and Irish Lions pair Rhys Webb and Biggar looking sharp and dangerous.
Webb's flat miss-pass sent Ashley Beck through on the left, but Rob McCusker was then unable to gather the centre's inside ball and the try chance went begging.
Biggar kept the Welsh side in touch with two penalties, the second a long-range effort with the clock red that trimmed Saracens' lead to 9-6 at half-time.
Worryingly for both Saracens and England, Vunipola did not emerge after the break because of a wrist injury, although the number eight did stay to watch the remainder of the match from the sidelines.
Ospreys had enjoyed an edge at the scrum in the first half and without Vunipola's bulk to anchor them the Saracens eight crumbled under a concerted shove, allowing Biggar to level the scores.
|Champions Cup Pool Two|
Farrell soon re-established Saracens' lead with a fourth successful kick, in the process become the fourth highest points scorer in European Cup history as he passed Diego Dominguez's mark of 645.
Despite trailing on the scoreboard Ospreys were bossing the second half, with locks Alun Wyn Jones and Bradley Davies, and flanker Justin Tipuric to the fore.
Saracens came under more pressure when replacement wing Chris Wyles was sin-binned on 66 minutes for taking out Sam Davies in the air.
Biggar kicked Ospreys level when Wales skipper Jones forced Saracens to hold on in the tackle, but with five minutes remaining Farrell edged the English side back in front once more.
The home scrum came to Ospreys' rescue once more, however, earning one last kick in the final minute that Biggar - after some discussion with captain Jones - coolly stroked between the uprights.
Ospreys now face the daunting task of going to face Clermont in France next week likely needing a win to qualify, but their fate is in their own hands.
Saracens are at home to Northampton, with the 2016 and 2017 European champions needing a big win in the all-English affair.
Ospreys head coach Steve Tandy said: "It's huge... a lot of it [qualification] is still in our control, we're not dependant on other results.
"It's about us going to France and hopefully scoring points and taking the game.
"We had a fully loaded Saracens team coming here, we were pretty patched up and the boys haven't done a lot of training this week.
"So I'm just super proud of this group... we just stayed in there, we felt they'd give penalties away and we could knock them over. It's not always about scoring four tries."
Saracens director of rugby Mark McCall said: "Billy Vunipola has an arm injury which we will obviously explore right away.
"I don't know what the extent of the injury is.
"Michael Rhodes has pulled a hamstring, so we had quite a lot to contend with. Our starting back-row were gone by half-time, and Jackson [Wray] went before the game, so there was a lot to deal with."
Ospreys: S Davies; Hassler, Beck, Watkin, D Evans; Biggar, Webb; Smith, Baldwin, Arhip, B Davies, AW Jones (capt), Cracknell, Tipuric, McCusker.
Replacements: Otten, Thomas, Fia, Beard, W Jones, Habberfield, Fonotia, Howells.
Saracens: Goode; Maitland, Marcelo, Barritt, Williams; Farrell, Wigglesworth; M Vunipola, George, Koch, Itoje, Skelton, Rhodes, Wray, B Vunipola.
Replacements: Tolofua, Barrington, Figallo, Kruis, Clark, Spencer, Lozowski, Wyles.
Referee: John Lacey (Ireland)
Assistant referees: David Wilkinson (Ireland), Eddie Hogan O'Connell (Ireland)
TMO: Kevin Beggs (Ireland)