Sale (8) 21
Tries: Martens, Robinson
Pens: Thomas (3)
Llanelli (5) 5
Scarlets coach Phil Davies' decision to rest six internationals proved decisive as Sale romped to a place in the semi-finals of the Anglo-Welsh Cup.
Sililo Martens opened the scoring, cancelled out when Iestyn Thomas went over for the Scarlets, shortly after Aled Gravelle had a try disallowed.
Sale's half-time lead grew when Lee Thomas replaced Daniel Larrechea, whose first-half kicking had been poor.
Jason Robinson added a late solo effort to seal a deserved victory for Sale.
Sale director of rugby Philippe Saint Andre:
"We missed 15 points and dropped the ball a few times close to the line. We needed to punish them.
"We didn't panic. We were patient and showed a lot of character. We defended well and Lee Thomas kicked very well.
"For the first time since the first game we didn't have anyone badly injured. It's good for our confidence."
Scarlets director of rugby Phil Davies:
"We were poor, not what we've come to expect, and we're disappointed to go out of the competition.
"We didn't have enough ball. Sale deserved to win.
"We came here with a group of players who won nine points out of 10 in the Magners League. It's about managing the big picture. It's a long season."
Sale: Robinson; Cueto, Mayor, Thomas, Foden; Larrechea, Martens; Roberts, Titterrell, Turner, Schofield, Day, J. Fernandez Lobbe, Lund, Chabal.
Replacements: Bruno, Stewart, Bonner-Evans, Jones, Wigglesworth, I. Fernandez Lobbe, Hanley.
Llanelli Scarlets: B. Davies; James, King, Gavin Evans, Garan Evans; C. Thomas, Stuart-Smith; I. Thomas, Gravelle, Manu, Cooper, MacLeod, D. Jones, Bater, N. Thomas.
Replacements: J. Davies, Owen, A. Jones, G. Thomas, Afeaki, L. Davies, Watkins.
Referee: Rob Debney (Leicestershire)