The World Cup-winning German had fallen down the pecking order at the Emirates Stadium this season, with Gabriel Magalhaes, David Luiz, Pablo Mari and Rob Holding all preferred by Mikel Arteta.
Browsing: Shkodran Mustafi
Alexandre Lacazette scored the winner as Arsenal made it back-to-back Premier League victories with a 3-2 success away to Cardiff City on Sunday.
Cardiff twice came from behind to level the scores
It was an ominous warning sign for the Gunners, and sure enough they were behind just five minutes later when Sterling collected possession on the left flank before cutting inside and blasting his finish past Cech from the edge of the box for his 50th Premier League goal
Arsenal equalised 11 minutes later through Pierre-Emerick Aubameyang, playing a one-two with Danny Welbeck.
Troy Deeney missed a second-half penalty to get Watford back in the game as Petr Cech became the first goalkeeper to reach 200 Premier League clean sheets
Iwobi came on for Mesut Ozil in the 84th minute of the tie
Arsenal are in second place on the table and eight points behind Premier League leaders, Chelsea
For so long, Shkodran Mustafi appeared to be the unlikely match winner with his first goal in English football, but Andre Gray levelled up from the spot in added time for the Clarets
The pair, who join from Valencia and Deportivo La Coruna respectively, will cost Arsenal more than £50 million, taking their summer spending to over £80 million