Chris Fusaro went over for Glasgow's only try

The Warriors headed into the game two points clear at the top of the table and unbeaten in their last four outings, while Ospreys were also in strong form.

There was little between the sides during a first half that was dominated by the two teams' defences.

Duncan Weir put the visitors in front with a penalty goal after 15 minutes, but it remained that way for just six minutes.

Daniel Evans levelled the scores with the boot but there were no further points scored before half-time.

Ospreys made a flying start to the second period, however, to establish a lead that they would retain for the remainder of the match.

Dan Biggar's penalty put Ospreys 6-3 in front, before Ben John smashed over the line at the end of a slick passing move.

Biggar missed the conversion, but he was on target just shy of the hour after Rhys Webb gathered his own chip kick to scamper over.

By now, the rain was pouring in Swansea, allow few opportunities for either team to add to their points tally.

Chris Fusaro's converted try in the minutes that followed gave visitors Glasgow a fighting chance in the final quarter of the game, but Biggar's penalty goal nine minutes from the end established an 11-point deficit that the visitors were unable to put a dent in.

Glasgow coach Gregor Townsend said: "We were just unable to grab hold of the momentum in the second half. We gave them a cheap penalty and then they got a line break that led to a try and when you have a lead like that in poor conditions, it is easier for the team that is defending than the one trying to come back into the game. Every game we play there is pressure. We knew we had a tough run-in, with Connacht and Ospreys away followed by Ulster at home. We were not able to get the win at Ospreys. There will be a lot of determination next week to put in a better performance, we will need it. I have been watching Ulster and like Munster and Ospreys [the other two sides qualified for the play-offs] they are a quality side. We have to show we are of that quality too.

"We have a good record at Scotstoun, though. It is on the way to being a sell-out [with capacity increased to 10,000] which creates an excellent atmosphere. There will be a home semi-final on the line but the main thing for us is to play better."