The Ecuador international was charging down the right wing when he was abruptly halted by the France international, who leapt into the challenge fully committed but did not come close to making a connection with the ball.
Referee Michael Oliver checked the condition of the South American before dismissing the former Lorient man.
Koscielny has now been dismissed eight times in his career, with this the sixth occasion he has seen red in 291 appearances for Arsene Wenger's men.
5 - Laurent Koscielny has been red carded five times since his Premier League debut, no player has been shown more often in this period. Off pic.twitter.com/Zqfevj4Wsx— OptaJoe (@OptaJoe) May 21, 2017
This red is one of his most costly as it means he will miss the opportunity to turn out at Wembley next weekend, when the Gunners will tackle Chelsea in a bid to win their third FA Cup in the space of four years.
Hector Bellerin had opened the scoring in the must-win match - the final game of the Gunners' Premier League season - before Koscielny saw a straight red card for his terrible tackle on Valencia.