Arsenal confirmed the signing on 7 July 2010 and Koscielny was handed the club's number 6 shirt, previously worn by Philippe Senderos, who had moved to Fulham earlier in the summer. Wenger explained he bought Koscielny due to the fact he added height to the team and Arsenal were low on centre backs. Koscielny made his debut against Barnet in a pre-season friendly in July 2010. One month later in his competitive debut against Liverpool at Anfield, he was sent off in the 94th minute for a second bookable offence. Both of his yellow cards were shown beyond 90 minutes. The game ended in a 1–1 draw with both teams having debut players sent off. He scored his first goal for Arsenal on 11 September 2010, in a 4–1 win against Bolton Wanderers.