It was a game of two halves in Galway as Ospreys secured the win but failed to pick up the bonus point that would have given them a home semi-final next weekend.
Instead, they travel to Limerick on Saturday to face Munster at Thomond Park, having defeated then twice this season already.
Nevertheless, they go into the play-offs as the form team, unbeaten in the last seven after this win in the Galway wind.
They raced into a 24 point half-time lead as they made the most of the elements, scoring three tries, but were unable to build on it after the break as Connacht almost turned the game on its head.
The teams were welcomed onto the field by a raucous crowd at a packed Sportsground, before Dan Biggar got the game underway.
It was Biggar who opened the scoring with a long-range kick from just inside the Ospreys half with the Galway wind at his back after a penalty at the scrum in the sixth minute.
An Ospreys knock-on deep inside their own 22 then gave Connacht a platform from which to attack, probing left and then right before seemingly creating room for Bundee Aki out on the wing, only for Aly Muldowney’s pass to go behind his centre with the tryline beckoning.
It was proving to be a frantic affair with unforced errors and knock-ons galore, but after one such mistake the Ospreys destroyed Connacht at their own put-in, allowing Dan Baker to pick up. A good line-break from Ben John took his team deep into Connacht territory before the centre popped it to Biggar who went under the posts to score before adding the extras. That meant the Ospreys led 10-3 with 16 gone.
A well-worked lineout move saw the Ospreys extend their lead shortly before the half hour mark. Tyler Ardron won the ball on the Connacht 22, Baker carried well, and John cut the Connacht defence wide open running a great angle to score his third try in as many games, Biggar again converting.
Try number three came just 90 seconds later and it was Rhys Webb, celebrating the birth of his second child yesterday, who raced over after good work up the right from Dan Evans and Hanno Dirksen. The conversion was more difficult than the first two, but the outcome was the same, Biggar slicing the posts to make it 0-24.
Looking to seal the bonus point before half-time, a lineout 5m out gave them a chance to go for the line, and after the attempted drive was halted the ball was moved to Walker who stepped his man and tried to dive over but lost control of the ball as he reached for the line.
HALF-TIME: CONNACHT 0 OSPREYS 24
With the wind at their backs, Jack Carty got Connacht’s first points of the day with a straightforward penalty from in front of the posts 90 seconds after the restart and he doubled his tally from the 10m line as the clock moved past 50 minutes.
Making the most of the conditions, Connacht then grabbed their opening try, putting the ball into the corner and then rumbling over from 5m out, Eoghan Masterson touching down. Carty’s conversion brought the home team back to within 11 points with 25 to go.
Connacht then laid siege on the Ospreys line, using the conditions to pin their opponents back as the visitors struggled to get out of their half as the rain drove into their faces.
With the clock ticking down and news filtering through that both Glasgow and Munster had bagged a try bonus point in their wins over Ulster and the Dragons respectively, the Ospreys were forced to push for the fourth try if they wanted to book a home tie next weekend. However, the ball went to ground as they looked to play it out of their own 22 and Dennis Buckley was able to take advantage and score in the final minute, Carty converting, as they claimed a losing bonus point.
For the Ospreys, the focus now turns to Munster at Thomond Park next Saturday, and 80 minutes of rugby where bonus points won’t come into the equation.