Ashton Hewitt salvaged a 20-20 Pro14 draw for the Dragons against the Ospreys after George North was sent off.
Wales wing North scored the opening try but saw red after only 14 minutes for taking Hewitt out in the air at the Liberty Stadium.
Yet still the Ospreys looked set to hold on for only a third victory of the season.
They led 20-15 at the break after Sam Perry also went over and Stephen Myler scored 10 points with the boot, Hewitt and Leon Brown touching down at the other end.
The Dragons could not find a way through a resolute Ospreys defence until Hewitt slid over in the corner right at the end, Sam Davies missing a chance to win it when his conversion attempt sailed wide.
Connacht got the better of Irish rivals Ulster 26-20 in their penultimate match of the regular season at the Aviva Stadium.
John Porch and Kieran Marmion finished to give Connacht a 14-6 advantage at the interval, with Bundee Aki – making his 100th appearance for the club – and Jack Aungier dotting down in the second half.
Jacob Stockdale and Nick Timoney scored the Ulster tries but they slumped to a defeat ahead of a clash with leaders Leinster before the Final Series.