October 5, 2014 was a terrible day for Arsenal. Its first loss of the season came to Chelsea, in a match which cranked the thermostat on an already heated rivalry, and during the match, Mesut Özil hurt his knee -- specifically, by partially rupturing the outer band of his left knee joint. As matters developed, he was out for the rest of the calendar year and for what was arguably the low point of the season, the New Year's Day defeat to Southampton.
But he returned for the next match in a substitute role against Stoke (the Arnautovic-leveling-Debuchy game), and then from February 1 to March 1, scored two goals and added five assists in a crucial stretch of the season that saw Arsenal vault from fifth to third in the standings and start an unbeaten Premier League streak that would span ten matches and three full calendar months.
Though Özil still hasn't produced the goal and assist numbers fan envisioned when he signed with Arsenal in 2013, he's still had a catalytic effect on the team that is measurable in some discernible ways (3.1 key passes per game, to lead the team, and an 88.2 percent successful pass rate, second only to Santi Cazorla among midfielders and forwards) and merely meeting the eye test in other ways, based on what he uniquely does on and off the ball to set up teammates and confound defenders. The emergence of the "What Humans See/What Özil Sees" meme highlights his ability to make passes that conflate soccer and master classes in chess, and his alleged "bulking up" to better prepare for the Premier League's physicality appears to have transformed him into, if nothing else, an able custodian of the team's new tight-fitting Puma jerseys.
He had several transcendent moments during the season -- the free-kick goal vs. Liverpool, the whole delicious FA Cup Finals highlight reel, and the otherworldly back-heel flick vs. Hull which tragically didn't result in even a shot on goal, but still demands multiple views for its sheer brilliance.
Had Özil stayed healthy the entire season, he likely would have made more of an incontrovertible case for himself as a Player of the Year, with numbers to underscore his importance to the team. And, yes, the January lineup inclusion of Francis Coquelin and the subsequent brilliance of double pivot partner Santi Cazorla (previously covered by my colleagues) were key to the 2015 form that elevated Arsenal's league standing from the past few years. But Arsenal minus Özil is simply not the equal of Arsenal with Özil, and 2015 illustrated his indisputable importance to the team and its fortunes.