Magners League - Ulster 20 Scarlets 18:Ulster moved up to second in the Magners League with a sixth win in succession, the first time they have achieved such a league run since they won the title in 2006.
Tries in either half from Ian Humphreys, along with two conversions and penalties from Ruan Pienaar, brought Ulster their highly valuable four points though Scarlets, whose own play-off hopes may have suffered irreparable damage, pushed them close but had to settle for a losing bonus point.
With three games remaining, Brian McLaughlin's squad will need to keep their winning streak going, and play with more consistency, to secure their place, though their immediate thoughts will now be on Sunday week's Heineken Cup quarter-final clash with Northampton Saints.
After some poor tactical kicking from Pienaar and Paddy Wallace, which saw the ball go out on the full on two occasions, Ulster strayed offside just outside their 22-metre line and Stephen Jones slotted the three points after eight minutes.
Pienaar then tried a monster penalty effort from all of 55 metres but was wide with the effort and then saw his second penalty attempt from closer range also float away on the wind.
Ulster then sprang to life when a Pienaar pass saw Humphreys step between Lou Reed and Ben Morgan to then round Rhys Priestland and score under the posts. Pienaar's conversion made it 7-3 just before the half-hour mark.
Ulster may well have then extended their lead when Adam D'Arcy put Andrew Trimble into space and only a last-ditch covering tackle from Ben Morgan prevented a certain score.
Jones then narrowed Ulster's lead to a point after Simon Danielli was penalised for not rolling away at a ruck but two minutes later the visitors were punished for the same offence and Pienaar kicked his first successful penalty to give Ulster a 10-6 lead just after the half-hour mark.
The South African then stretched Ulster's lead further with a super strike from out on the left touchline after Scarlets had gone into a ruck from the side giving Ulster a 13-6 lead at the break.
But Scarlets hit back seconds after the restart when Jon Davies got past Danielli and D'Arcy to make the right corner.
Rhys Priestland, taking over the kicking duties from the substituted Stephen Jones, missed the difficult conversion.
Ulster then had an extremely fortunate escape after a Stoddart kicked through and was adjudged by the television match official to have knocked the ball on when trying to reclaim his kick before touching it down.
Things then took a turn for the worse for the west Wales side as Josh Turnbull was sent to the bin for illegal use of the boot after 49 minutes but the Scarlets survived his absence.
Then, seemingly from nothing, Humphreys scored his second after a great Danielli surge from out of his own half which was then driven on by Tom Court before Pienaar gifted the Ulster out half a stroll over the line.
The South African duly converted to put the home side 20-11 to the good and looking comfortable for the win.
But then Scarlets replacement Aaron Shingler got on the end of a Pienaar pass and scampered away for a try which Priestland converted to cut Ulster's lead to two points but the home side held on for the vital win.
Ulster: A D'Arcy; A Trimble, N Spence, P Wallace, S Danielli; I Humphreys, R Pienaar; T Court, R Best (capt), BJ Botha, J Muller, D Tuohy, R Diack, W Faloon, P Wannenburg. Replacements: A Kyriacou, P McAllister, D Fitzpatrick, T Barker, C Henry, P Marshall, I Whitten, C Gilroy.
Scarlets: R Priestland; G Maule, R King, J Davies, M Stoddart; S Jones, T Knoyle; I Thomas, M Rees (capt), R Thomas, L Reed, R McCusker, J Turnbull, J Edwards, B Morgan. Replacements: E Phillips, R Jones, P Edwards, A Shingler, D Lyons, M Roberts, D Evans, S Williams.
Referee: Graham Knox (Scotland).
