Allen Clarke's first PRO14 game in charge of the Ospreys ended in a 26-15 defeat to Conference A rivals Connacht at the Sportsground.
Flanker Eoghan Masterson's try on the stroke of half-time gave Kieran Keane's men a 13-5 lead, as they looked to make it seven successive home wins in all competitions.
Apart from Dafydd Howells' well-taken 18th-minute try, Connacht's defence managed to frustrate Ospreys who had dominated first half possession.
Ospreys coped well during Hanno Dirksen's sin-bin period, Sam Davies swapping penalties with Connacht's man of the match Craig Ronaldson, before tries at either end from Tom Farrell and Reuben Morgan-Williams. Ronaldson sealed victory with his fourth penalty of the night.
Fly-half Ronaldson, who was returning from injury, converted the second of two early penalty attempts for a 3-0 lead, the province threatening a try when Caolin Blade was stopped five metres out by Lloyd Ashley's high tackle.
A Blade kick was then blocked down by Sam Davies as Ospreys sought a quick response. They turned down a kickable penalty but a Ronaldson interception foiled the Welshmen, who recently parted company with long-serving head coach Steve Tandy.
Connacht came under further pressure with Tiernan O'Halloran and Andrew Browne both leaving the field injured, and finding space out wide, Ashley Beck and Kieron Fonotia combined to release Howells who produced a fine finish in the corner past the despairing Pita Ahki.
Davies was unable to converted and Ronaldson kicked Connacht back in front with a 24th-minute penalty. Again, the visitors turned down a shot at the posts in response, the decision not paying off as Fonotia knocked on.
Despite Tom Habberfield's influence on the ball, two costly penalties - one of them forced by centre Farrell's breakdown work - ended promising spells from Ospreys, and Connacht stung them with a try via a late lineout opportunity.
The home forwards carried strongly, hooker Tom McCartney in particular, before Blade fed Masterson to drive low and score to the left of the posts, with Ronaldson converting.
The Ospreys' task grew more difficult after they missed out on an early second half try - Dirksen's return pass to Davies went forward - and the right winger then saw yellow for a late tackle, 52 minutes in.
Davies pulled a penalty wide before redeeming himself to close the gap back to 16-8, with Dirksen returning from the bin. However, poor defending from Davies and Beck who allowed Farrell to slip away from them saw the latter dart clear for a well-taken 68th-minute try, converted by Ronaldson.
Although Habberfield's replacement Morgan-Williams raised Ospreys' hopes by scrambling over three minutes later -- the home crowd did get on referee Stuart Berry's back over a questionable grounding -- it was fittingly left to Ronaldson's left boot to sew up the result and complete his own 16-point haul.