Collins double helps Scarlets down Ulster
Collins scored two first-half tries for the Scarlets, but Ulster were able to go in ahead at half-time thanks to scores from Craig Gilroy and Luke Marshall.
The second half wasn't as open but remained just as tense, with Aled Thomas' boot doing just enough to kick the Scarlets to victory.
The Scarlets made the perfect start with a try after just four minutes. It came after the visitors had held onto the ball for an extended period of time.
Ulster held well initially but eventually the pressure told and when the Scarlets created an overlap, Hadleigh Parkes took advantage to cut inside Darren Cave before feeding Collins for the try.
Aled Thomas missed the conversion, but was on target with a penalty after Ulster were penalised for hands in the ruck.
The deficit was cut back to five points by skipper Paddy Jackson with a snap drop goal, and he gave the home side the lead with a fine conversion after an even better try by Gilroy.
The wing got the ball out on the right but still had 60 metres and a lot of work to do. He showed his pace and some silky footwork to chip over Collins and collect before outpacing Gareth Owen to the line. With Jackson's 
extras, Ulster led 10-8 after 20 minutes but the lead did not last long.
A fine break from Owen got the Scarlets back on the front foot, and Thomas then sliced through after the ball had been recycled. A knock-on from Jackson gave the Scarlets an advantage and they showed great hands to ship the ball to the left for Collins to complete a double. This time Thomas was on target with his conversion to make it 15-10.
However, just before half-time Ulster moved back in front with another great try. Playing with penalty advantage Paul Marshall sniped away at a ruck and then threw the wide pass to Luke Marshall for the score in the corner despite a convergence of Scarlets defenders.
Jackson again converted from the touchline, to put Ulster back in front, and that was in sharp contrast to Thomas, who hit the post with a penalty effort right on the stroke of half-time after Ulster had been caught offside at a breakdown.
The Scarlets should have had their third try right at the start of the second half but couldn't quite finish off after wonderful hands had put Collins away. He found DTH van der Merwe inside him but the Canadian was scragged just short of the line. The ball then went right and back left but with Regan King over the line, he couldn't touch down and the knocked on as he tried to offload.
Still, Ulster failed to clear to touch and after another series of attacks, the home side were penalised for slowing the ball, allowing Thomas to slot the penalty and put the Scarlets back in front.
Ulster's indiscipline was proving problematic and they lost Chris Henry soon after to the sin-bin when he was penalised for handling the ball at a ruck. Thomas added another three points to stretch the Scarlets' lead to 21-17.
Trailing by four, Ulster turned down a shot at goal soon after, instead kicking to the corner. It didn't pay off though as the Scarlets defended well and were able to clear.
However the Scarlets couldn't manage any more points while Henry was off, and he returned just as they went back to the corner follow an infringement in a ruck.
They couldn't make that count but when the Scarlets were penalised for failing to roll away, Jackson slotted the simple penalty to make it a one-point game.
Ulster threw everything at the Scarlets in the last 10 minutes, but with five to go the visitors got hold of the ball and they were able to see out the game and secure the four points.
The scorers:
For Ulster:
Tries: Gilroy, Marshall
Cons: Jackson 2
Pens: Jackson
DG: Jackson
For Scarlets:
Tries: Collins 2
Cons: Thomas
Pens: Thomas 3
Yellow card: Chris Henry (Ulster, 48)
Teams:
Ulster: 15 Stuart Olding, 14 Craig Gilroy, 13 Darren Cave, 12 Luke Marshall, 11 Jacob Stockdale, 10 Paddy Jackson (captain), 9 Paul Marshall, 8 Roger Wilson, 7 Chris Henry, 6 Robbie Diack, 5 Franco van der Merwe, 4 Alan O'Connor, 3 Ricky Lutton, 2 John Andrew, 1 Andrew Warwick.
Replacements: 16 Johnny Murphy, 17 Kyle McCall, 18 Bronson Ross, 19 Pete Browne, 20 Clive Ross, 21 Ruan Pienaar, 22 Ian Humphreys, 23 Sammy Arnold.
Scarlets: 15 Michael Collins, 14 Gareth Owen, 13 Regan King, 12 Hadleigh Parkes (captain), 11 DTH van der Merwe, 10 Aled Thomas, 9 Aled Davies, 8 Morgan Allen, 7 Will Boyde, 6 Aaron Shingler, 5 David Bulbring, 4 George Earle, 3 Peter Edwards, 2 Kirby Myhill, 1 Phil John.
Replacements: 16 Ryan Elias, 17 Dylan Evans, 18 Rhodri Jones, 19 Maselino Paulino, 20 Rory Pitman, 21 Rhodri Williams, 22 Dan Jones, 23 Steffan Evans.
Referee: Ian Davies (Wales)
Assistant referees: Nigel Correll (Ireland), John Carvill (Ireland)
TMO: Alan Rogan (Ireland)
