By Jamie Spencer Arsenal manager Mikel Arteta has pinpointed the individual quality of Lionel Messi as one of the reasons the Gunners haven’t been beyond the last 16 of the Champions League since 2010. As a player, Arteta was part of an Arsenal squad knocked out at the last 16 in all of his five seasons at the club – the same happened the year before his 2011 arrival and the year after his 2016 retirement to make it seven straight exits in the first knockout round. Now, as Arsenal boss leading the team into their first Champions League knockout game in seven years against Porto, Arteta has den…