Jonny Fa'amatuainu scored a hat-trick as the Scarlets opened up their LV= Cup campaign with a 52-13 win over Leeds Carnegie at Parc y Scarlets.
In his first start for the region since moving from Bath on loan, the Samoan blindside was on hand to score three of his side's seven tries.
A young Leeds team which included 17-year-old lock Dominic Barrow could not deal with the pace of the Scarlets, who included Wales squad wing George North.
North played for an hour in what was his first rugby for almost a month since he fractured his ankle against the Ospreys at the beginning of October.
The first half was a nip and tuck affair until the Scarlets hit Leeds with three tries in the space of seven minutes.
First Fa'amatuainu, who was on hand to follow up Scott Williams' kick through for his first score, was on North's shoulder to go over before Williams ran in from the halfway line after an initial burst by Dan Newton.
And on the stroke of half-time Newton was put over for the bonus-point try after good work by number eight Ben Morgan and lock Aaron Shingler.
Leeds had been in the game during the first quarter and had led 13-7 thanks to a try from former Wales squad scrum-half Warren Fury, who nipped in at the blindside.
After the scoring burst in the second quarter, the first 20 minutes after the break proved scoreless.
Leeds pressed the Scarlets line but the home defence held firm.
At the other end the Scarlets twice wasted golden opportunities until Fa'amatuainu completed his hat-trick following a break by lock Dominic Day.
The English side's frustrations were summed up when replacement flanker Oliver Stedman was sin-binned for not rolling away at a ruck.
And with the extra man the Scarlets went in for their sixth try through Shingler in injury time before centre Williams went over for his second score.
Williams' try, in the fourth minute of added time, took his side past 50 points and meant the Scarlets had piled on 45 unanswered points.
Tries: Fa'amatuainu 3, Williams 2, Newton, Shingler
Con: Newton 4, Shingler 3
For Leeds Carnegie:
Pen: Lewis-Pratt 2
Scarlets: 15 Daniel Evans, 14 George North, 13 Nick Reynolds, 12 Scott Williams, 11 Lee Williams, 10 Dan Newton, 9 Gareth Davies, 8 Ben Morgan, 7 Richie Pugh, 6 Jonny Fa'amatuainu, 5 Aaron Shingler, 4 Vernon Cooper, 3 Peter Edwards, 2 Ken Owens (capt), 1 Phil John.
Replacements: 16 Rhys Lawrence, 17 Rhodri Jones, 18 Simon Gardiner, 19 Dominic Day, 20 Nic Cudd, 21 Martin Robers, 22 Steven Shingler, 23 Lee Rees.
Leeds Carnegie: 15 Leigh Hinton, 14 James Tincknell, 13 Henry Fa'afilli, 12 Luther Burrell, 11 Semi Tadulala, 10 Christian Lewis Pratt, 9 Warren Fury, 8 Alfie Tooala, 7 Kearnan Myall (capt), 6 Danny Paul, 5 James Craig, 4 Dominic Barrow, 3 Phil Swainston, 2 Phil Nilsen, 1 Mike MacDonald.
Replacements: 16 Miguel Alonso, 17 Gareth Denman, 18 Jesus Moreno-Rodriquez, 19 Oliver Stedman, 20 Chris Walker, 21 Craig Hampson, 22 Peter Wackett, 23 Oliver Denton.