ST ALBANS, ENGLAND - SEPTEMBER 18: (L-R) Calum Chambers and Per Mertesacker of Arsenal warm-up during a training session at London Colney on September 18, 2015 in St Albans, England. (Photo by Stuart MacFarlane/Arsenal FC via Getty Images)
ST ALBANS, ENGLAND - SEPTEMBER 18: (L-R) Calum Chambers and Per Mertesacker of Arsenal warm-up during a training session at London Colney on September 18, 2015 in St Albans, England. (Photo by Stuart MacFarlane/Arsenal FC via Getty Images)