Fly-half Sam Costelow will make his first Pro14 start for Scarlets when they host Leinster on Saturday.

Versatile Wales back Johnny McNicholl moves from wing to full-back and Uzair Cassiem is back at number eight.

Leinster's Tadhg Furlong returns to play his first match in almost a year.

The prop has not played since Ireland's Six Nations defeat by England in February because of calf and back problems, while it is over a year since he has played for his club.

Max O'Reilly makes his second appearance at full-back, with Cian Kelleher on the right wing and Dave Kearney returning on the left after missing the win over Munster with a minor hamstring injury.

Furlong is joined in the front row by Peter Dooley and James Tracy, while there is a chance of a debut off the bench for 19-year-old centre Jamie Osborne.

Leo Cullen's side go into the match on the back of a close comeback win over Munster on their return to Pro14 action last week.

The hosts are missing 11 Wales Six Nations squad members.

Glenn Delaney's side are also without injured players Sione Kalamafoni (concussion), Steff Evans (leg), Lewis Rawlins (neck), Tomi Lewis (knee), Dylan Evans (shoulder), Samson Lee (concussion), Jac Morgan (knee), Tom Rogers (knee), Pieter Scholtz (hamstring), Rob Evans (concussion) plus long-term absentees James Davies (concussion), Aaron Shingler and Rhys Patchell.

Ryan Conbeer and Tom Prydie come on to Scarlets' wings, with Tyler Morgan joining skipper Steff Hughes at centre, while Dane Blacker is at scrum-half.

Phil Price and Marc Jones join Javan Sebastian in the front row, with Morgan Jones partnering Sam Lousi at lock.

Cassiem will make his 50th Scarlets appearances as he takes over from concussed Kalamafoni at number eight, while Dan Davis is back at open-side flanker after an ankle problem.

The game has been rearranged after it was postponed in December because of Covid-19.

Scarlets have suffered back-to-back defeats against Cardiff Blues, while defending Champions Leinster won 13-10 at Munster and are second in Conference A.

Scarlets head coach Glenn Delaney said: "You look at the games against Connacht, Ulster and then into Bath before Christmas, we were in a purple patch and playing the rugby we wanted to. The derbies have been a little disjointed. This gives us a chance to refresh, reset and get back to where we were.

"Leinster defend differently to Cardiff. We have got a plan to create and there will be opportunity for guys who haven't been playing these past few weeks. That is bringing new energy and excitement to the group. Our job is to make sure they are free and are able to express themselves.

"When you play Leinster you have to make sure you remain in the contest to give yourself a chance to execute. We know they are the form horse, they have been for a number of years and they have plenty of depth. It is an opportunity to have a crack at them and we are excited by it."

Scarlets: Johnny McNicholl; Tom Prydie, Tyler Morgan, Steff Hughes (capt), Ryan Conbeer; Sam Costelow, Dane Blacker; Phil Price, Marc Jones, Javan Sebastian, Morgan Jones, Sam Lousi, Blade Thomson, Dan Davis, Uzair Cassiem.

Replacements: Taylor Davies, Kemsley Mathias, Werner Kruger, Tevita Ratuva, Carwyn Tuipulotu, Will Homer, Angus O'Brien, Paul Asquith.

Leinster: Max O'Reilly; Cian Kelleher, Liam Turner, Ciaran Frawley, Dave Kearney; Harry Byrne, Luke McGrath (capt); Peter Dooley, James Tracy, Tadhg Furlong, Ross Molony, Ryan Bair, Josh Murphy, Dan Leavy, Jack Conan.

Replacements: Sean Cronin, Ed Byrne, Tom Clarkson, Jack Dunne, Scott Fardy, Hugh O'Sullivan, David Hawkshaw, Jamie Osborne.

Referee: Mike Adamson (SRU)

Assistant referees: Craig Evans, Dan Jones (both WRU)

TMO: Jon Mason (WRU)