Pienaar quickly restored Ulster's four point gap with his first penalty off the game and he added another two minutes later to give his side a 7 point lead.
Half time: 13-6
The Scarlets made a great start to the second half with a try 42 seconds after the restart from centre Jon Davies. Regan King fed his midfield partner who had the pace to outstrip the Ulster defence and score in the corner but Priestland couldn't convert.
Stoddart had a try disallowed by the TMO as he collected his own grubber kick to touch down but he was ruled to have knocked the ball on going over the line.
The Scarlets had flanker Josh Turnbull sin binned on 50 minutes for illegal use of the boot but despite winning a couple of penalties and kicking for touch, Ulster couldn't make their numerical advantage count.
Humphreys scored his second try on 63 minutes after Ulster had absorbed a sustained period of pressure. Danielli picked the ball up from the base of a ruck and went into the Scarlets 22 and Tom Court carried the ball closer to the try line. The ball was then spun wide for Humphreys to go over with Pienaar converting to push them further ahead (20-11).
The Scarlets made it a nervy last couple of minutes for Ulster when replacement flanker Aaron Shingler intercepted a pass from Pienaar and went over unopposed. Priestland added the conversion but Ulster were able to close the game out with a 20-18 scoreline..
|Ulster Rugby Score Card|
|Scarlets Score Card|