England flanker Hendre Fourie scored a try on his home debut to give Sale a 19-14 victory but Scarlets were still able to progress to the semi-finals of the LV= Cup.
Scarlets' bonus point, coupled with defeats for their pool rivals Gloucester and Newcastle, guaranteed their passage into the last four. But they will need to improve on their performance in the semi-finals, after being on the back foot for most of the match in the north-west.
Welsh fly-half Nick Macleod kicked 14 points against his compatriots while Fourie had an outstanding game on his first match at Edgeley Park since his move from Leeds in the summer.
After winning their first three games in the competition, the Scarlets went into the match knowing destiny was in their own hands. They also had the benefit of including Stephen Jones, Liam Williams, Aaron Shingler, Lou Reed and Rhodri Jones on the bench following their release from Wales duty. But it was the home team, who had lost their previous three games in the competition, who made the brighter start.
The Sharks were rewarded with the game's opening try in the ninth minute. After Macleod kicked a penalty to touch, Sale's pack mauled their way towards the line from the lineout and Fourie touched down. Fly-half Macleod added the extras but following a mistake by Dwayne Peel inside the Sale 22, Scarlets won a penalty and Dan Newton opened his account with a 16th-minute penalty.
Newton added a second in the 27th minute following more pressure from Nigel Davies' side, the visitors took the lead just before the break. The Sale defence was caught cold by a quick tap penalty and Scarlets took advantage by moving the ball quickly via winger Andy Fenby out to Peter Edwards, who powered over from close range.
Newton was unlucky to miss the resulting conversion, his kick coming back off the posts from a tight angle near the right touchline leaving the game tantalisingly poised at 11-7.
Much like in the first period, the Sharks started the half brightly and despite missing one penalty, Macleod nailed the second from closer range to reduce the deficit to a solitary point. The fly-half was having a decisive influence on affairs as was Fourie, who seemed to be letting out several months of frustration after his injury setbacks.
Two further penalties from Macleod made it 16-11 just after the hour mark and after Scarlets were off-target with a kickable penalty, Stephen Jones, on as a replacement, did reduce the deficit with 10 minutes remaining.
The game remained in the balance right until the final stages until another MacLeod penalty secured the victory but it was the Scarlets who progressed.