Pienaar earned Ulster an 18-16 triumph at Parc y Scarlets earlier in the year with a 50 metre penalty and his last gasp drop shot came moments after Jason Tovey had seemingly won the game for the Dragons with a drop goal of his own.
That made it 23-22 to the visitors, who had matched the home side try for try with touchdowns from Tovey, Lewis Evans and Aled Brew, but Ulster regathered the kick-off, moved to within striking distance and then watched as their South African import won the day.
It was a bitter blow for the Dragons’ Play-Off hopes, although they still have a chance of making the top four. Five of their remaining six games at are home and they still have to play four teams above them at Rodney parade – Blues, Ospreys, Leinster and Ulster.
The bonus point at Ravenhill moved the Dragons into seventh place, but left them 17 points adrift of Ulster in the fourth Play-Off spot. They are also 12 points behind the sixth placed Scarlets in the race for the third and final automatic qualifying spot for the Heineken Cup.
Magners League P W D L Pts
1 Munster 17 14 0 3 63
2 Ospreys 17 11 0 6 54
3 Leinster 17 11 1 5 51
4 Ulster 17 11 1 5 51
5 Blues 16 11 0 5 49
6 Scarlets 17 9 1 7 46
7 Dragons 16 7 1 8 34
