|Racing Metro (15) 18|
|Tries: Imhoff, Thomas Con: Goosen Pens: Goosen (2)|
|Ospreys (0) 14|
|Tries: Webb, Walker Cons: Biggar (2)|
Racing Metro fought off a spirited second-half comeback by Ospreys to leave the Welsh side's European hopes hanging by a thread with victory in Le Mans.
The French side led 15-0 at half-time as wingers Juan Imhoff and Teddy Thomas both crossed within three minutes.
After the break, Rhys Webb and Eli Walker tries, converted by Dan Biggar, made it 15-14.
But Johannes Goosen's late penalty sealed the win for Racing.
Ospreys are now third in Pool five with two games to go, six points behind second-placed Racing and seven behind leaders Northampton.
Both sides had targeted the match at the MM Arena as a must-win in their bid to catch the English club, who beat Treviso 67-0.
The Welsh region, who earned a 19-19 draw late on against the French side last Saturday were quick out of the blocks and took the game to their hosts, but handling errors at key moments proved costly.
Steve Tandy's team were down to 14-men within 10 minutes as scrum-half Rhys Webb saw yellow for a late and high tackle on Racing wing Juan Imhoff. Johannes Goosen kicked the resulting penalty.
Racing failed to capitalise on their numerical advantage, but moved up a gear to take control shortly after Webb returned to the field 10 minutes later.
The French-side's pack began to dominate and, following a series of scrums close to Ospreys' line, Racing went through several phases to work an overlap for Imhoff to score, with Goosen converting.
Ospreys found themselves further behind just three minutes later as hooker Scott Baldwin failed to collect Webb's pass deep inside the Racing half.
The French made the Welsh region pay, swiftly spreading the ball wide in a clinical counter attack from their own half, which ended with Thomas scoring in the corner.
Ospreys showed patches of what was to come after the break.
Full-back Dan Evans sliced through the Racing defence, but his pass failed to find flanker Justin Tipuric in support midway inside 22, as Ospreys trailed 15-0 at half-time.
Seconds after the break, the Welsh side were given a boost as Racing number eight Antonie Classen was sent to the sin bin for taking out Biggar in the air.
Ospreys spurned a kickable penalty shortly afterwards, opting to kick for the corner as they chased the game, but lost the resulting line out inside Racing's 22.
As Classen returned to the field, Racing scrum-half Maxime Machenaud saw yellow for a deliberate knock-on to thwart an Ospreys' attack.
Webb darted through a small gap in the Racing defence to give the Welsh side hope, with Biggar adding the conversion.
The game broke up and became unstructured leading to several breathless passages of play as Ospreys went for broke.
One of which saw Racing run the ball 80m from behind their own try line after turning over an Ospreys' driving maul.
With 10 minutes to go, Walker beat three Racing defenders to crash over the line, after catching a Biggar cross-kick, who added the conversion to make it 15-14.
Ospreys continued to press, but Racing held on and Goosen's penalty put the game beyond the Swansea-based side in injury time.
Racing Metro: Brice Dulin; Juan Imhoff, Henry Chavancy, Jamie Roberts, Teddy Thomas; Johannes Goosen, Maxime Machenaud; Julien Brugnaut, Dimitri Szarzewski (capt), Luc Ducalcon, Juandre Kruger, Francois van der Merwe, Wenceslas Lauret, James King, Bernard Le Roux, Antonie Claassen.
Replacements: Charteris for Kruger (19), Arous for Brugnaut (60), Lacombe for Szarzewski (60), Mujati for Ducalcon (60), Phillips for Machenaud (61), Audrin for Imhoff (72).
Not used: Gerondeau.
Sin bin: Classen (41) and Machenaud (50).
Ospreys: Dan Evans; Hanno Dirksen, Ashley Beck, Josh Matavesi, Eli Walker; Dan Biggar, Rhys Webb; Marc Thomas, Scott Baldwin, Dmitri Arhip; Rynier Bernardo, Alun Wyn Jones (capt); James King, Justin Tipuric, Tyler Ardron.
Replacements: Gareth Thomas for M Thomas (68) and Sam Davies for Evans (68).
Not used: Sam Parry, Daniel Suter, Olly Cracknell, Martin Roberts, Andrew Bishop.
Sin bin: Webb (10).
Referee: Greg Garner (England)