Extra time had ended 1-1, with Chelsea bringing on Kepa for Mendy in the final seconds in what turned out to be the game's tactical master-stroke
Goalkeeper Kepa Arrizabalaga came off the bench to make two shootout saves as Champions League winners Chelsea beat Spain's Villarreal 6-5 on penalties to add the Uefa Super Cup to their trophy collection Wednesday.
Extra time had ended 1-1 at Belfast's Windsor Park stadium, with Chelsea bringing on Kepa for Edouard Mendy in the final seconds in what turned out to be the game's tactical master-stroke.
The freshest player on a field of tired legs saved first from Aissa Mandi at 1-1, after Kai Havertz had missed for Chelsea, and then made the winning stop at 6-5 when Villarreal captain and 2010 World Cup winner Raul Albiol hit the ball to the bottom left.
Mendy was one of the first to congratulate his team mate, with Chelsea lifting the trophy for a second time.
Mendy said he had no hard feelings at all.
Hakim Ziyech had put Chelsea ahead in the 27th minute, sweeping in from 12 yards after a perfectly measured cross from Havertz on the left.
The Morocco international, an unused substitute when Chelsea beat Manchester City 1-0 in the Champions League final in Porto on May 29, then went off injured four minutes before the break following a collision with Juan Foyth.
Ziyech returned with his right arm in a sling to watch the rest of the match from the bench while Christian Pulisic took his place.
Villarreal, the Europa League holders with a noisy contingent of some 1,000 fans among the 13,000-strong crowd on a clear evening in Northern Ireland, hit the woodwork either side of halftime.
Their equalizer came as no surprise in a lively match with several scoring chances squandered on both sides and both keepers making key saves.
Gerard Moreno - who scored against Manchester United before the Europa League final in Gdansk went to penalties - rescued Unai Emery's side in the 73rd with a side-foot finish after a back-heel from Boulaye Dia.
It was Moreno's eighth goal in his last nine European appearances for Villarreal.
Pulisic had a good chance in the 99th, the ball just running wide, while Mason Mount had a shot pushed out for a corner in the 108th.
Chelsea now turn their thoughts to the start of the Premier League season, and the imminent signing of striker Romelu Lukaku from Inter Milan, with an opening match at home to Crystal Palace Saturday.