Ospreys defeated 14-man Scarlets in the United Rugby Championship after Argentina flanker Tomas Lezana was shown a fifth-minute red card.

Scarlets responded with tries for Sione Kalamafoni and Johnny McNicholl.

It was just Ospreys' second league win of the season.

In front of a crowd of 11,480 in Swansea, Webb impressed again as he bids for a Wales recall, while flanker Jac Morgan was named player of the match to mark an outstanding display against his former side.

The victory lifted Ospreys one place to 13th in the URC table, while Scarlets remain languishing in 15th, with only Zebre below them.

Both teams had come into the game with only one win in the URC so far this season but on the back of victories in European competition.

They were also both forced into late changes. Following the Champions Cup success at French champions Montpellier, Ospreys brought in a new-look front row of Nicky Smith, Scott Baldwin and Tomas Francis, while Morgan was also included.

The home side suffered a late blow with the withdrawal of captain Justin Tipuric who was replaced by Ethan Roots, with Webb taking over the leadership reins.

Captain Jonathan Davies was the Scarlets' only initial change from the team that defeated Cheetahs in the Challenge Cup as he replaced centre Scott Williams.

But there proved a late alteration following the withdrawal of lock Sam Lousi following the birth of his child.

This forced a late reshuffle with Kalamafoni moving up to the second row and Josh Macleod starting at number eight.

Lezana started but was not on the field for long as he was shown the red card for a high tackle on Rhys Davies with the pair clashing heads.

Davies was forced off the field temporarily, replaced by Alun Wyn Jones, before returning.

The home side took advantage with a well-worked try for Wales wing Cuthbert.

The Ospreys' scrum was dominating a Scarlets pack that was missing a specialist forward following Lezana's departure.

This forced the visitors to bring on second row Tom Price for wing Steff Evans.

Ospreys took advantage of where Evans would have been defending with wing Morgan sliding over for the second try in the left corner, Owen Williams converted.

Scarlets were forced into more disruption with prop Javan Sebastian replacing Will GriffJohn.

Morgan almost scored a superb individual try, but after choosing not to pass, the Ospreys wing was denied by an excellent covering tackle from Scarlets lock Vae'a Fifita.

Ospreys were temporarily reduced to 14 men when Williams was shown a yellow card for a high tackle on opposite number Sam Costelow, who was forced off the field because of the challenge.

Referee Craig Evans decided it was not a red card because he deemed it a passive tackle and adjudged that Costelow stepped into the tackle.

With the numbers of players evened up, Kalamafoni powered over to open the Scarlets account, with replacement Rhys Patchell converting.

Ospreys rallied with an outstanding individual effort from Webb who sprinted through the heart of the Scarlets defence for a try which he also converted, with Williams off the field as the hosts led 19-7 at half-time.

Scarlets were handed a gift after McNicholl intercepted a Webb pass and outflanked Michael Collins to score, with Patchell adding the touchline conversion.

This brought the Scarlets to within a score but Williams slotted over a penalty to extend the advantage to eight points.

Webb thought he had scored his second try but was held up by Scarlets replacement Price.

The bonus-point try eventually came when replacement hooker Parry was driven over.

Centre Williams provided the fitting finale with the final try after being released by fellow centre Collins.

Ospreys head coach Toby Booth: "It was very important to kick on after last week's performance against Montpellier and we probably thought we did not have the rub of the green in certain performances.

"To get the win and the manner of it, in how we went about our work, was impressive on the back of last week.

"We know how committed derbies are, we managed to navigate through it and come out on top."

Scarlets head coach Dwayne Peel: "It makes it difficult to play 75 minutes with 14 men but I felt at 22-14 we were right in it.

"We got caught in our half three times and they resulted in Ospreys' points.

"We turned over ball in the middle of the park where Jac Morgan was excellent on the floor.

"We put ourselves in the position to win it, or get close, but there were some fundamental errors and that is the game in derbies."

Ospreys: Max Nagy; Alex Cuthbert, Michael Collins, Keiran Williams, Luke Morgan; Owen Williams, Rhys Webb (capt); Nicky Smith, Scott Baldwin, Tomas Francis, Rhys Davies, Adam Beard, Ethan Roots, Jac Morgan, Morgan Morris.

Replacements: Sam Parry, Gareth Thomas, Tom Botha, Alun Wyn Jones, Huw Sutton, Reuben Morgan Williams, Jack Walsh, Joe Hawkins.

Scarlets: Johnny McNicholl; Steff Evans, Ioan Nicholas, Jonathan Davies (capt), Ryan Conbeer; Sam Costelow, Dane Blacker; Kemsley Mathias, Ryan Elias, WillGriff John, Vaea Fifita, Sione Kalamafoni, Aaron Shingler, Tomás Lezana, Josh Macleod.

Replacements: Ken Owens, Steff Thomas, Javan Sebastian, Tom Price, Carwyn Tuipulotu, Kieran Hardy, Rhys Patchell, Scott Williams.

Referee: Craig Evans (WRU)

Assistant referees: Rhys Jones (WRU), Gwyn Morris (WRU)

TMO: Jon Mason (WRU)