Saracens ended the Ospreys' six year unbeaten record at home in the Heineken Cup to seize the initiative in Pool Five with a 13-16 victory at the Liberty Stadium.
Ernst Joubert's opportunist first-half try and 11 points from the boot of Owen Farrell proved enough to claim victory for the English Champions.
Farrell and Dan Biggar traded early penalties in a tight opening before Ospreys flyhalf Biggar saw his clearance kick charged down by Charlie Hodgson, setting up Joubert for the game's opening try.
Farrell had no problems with the conversion and he then kicked a further penalty for Saracens before the break.
Ashley Beck twice went close as Ospreys rallied early in the second half before former Wales lock Ian Gough touched down for his first European try,
Biggar converted to narrow the lead the three points with 15 minutes remaining but Heineken Cup winner Peter Stringer used all his experience from countless campaigns with Munster to help Saracens close out the game, and with it a crucial win.
Pens: Biggar 2
Pens: Farrell 3
Ospreys: 15 Richard Fussell, 14 Tommy Bowe, 13 Andrew Bishop, 12 Ashley Beck, 11 Shane Williams, 10 Dan Biggar, 9 Rhys Webb, 8 Jonathan Thomas, 7 Justin Tipuric (captain), 6 Ryan Jones, 5 Ian Evans, 4 Ian Gough, 3 Adam Jones, 2 Richard Hibbard, 1 Paul James.
Replacements: 16 Huw Bennett, 17 Duncan Jones, 18 Aaron Jarvis, 19 Joe Bearman, 20 George Stowers, 21 Kahn Fotuali'i, 22 Matthew Morgan, 23 Hanno Dirksen.
Saracens: 15 Alex Goode, 14 David Strettle, 13 Owen Farrell, 12 Brad Barritt, 11 Chris Wyles, 10 Charlie Hodgson, 9 Ben Spencer, 8 Ernst Joubert, 7 Jacques Burger, 6 Kelly Brown, 5 Mouritz Botha, 4 Steve Borthwick (captain), 3 Matt Stevens, 2 Schalk Brits, 1 Rhys Gill.
Replacements: 16 John Smit, 17 Deon Carstens, 18 Carlos Nieto, 19 George Kruis, 20 Andy Saull, 21 Peter Stringer, 22 Adam Powell, 23 James Short.
Referee: Jerome Garces
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