Arsenal, oh typical Arsenal. Arséne Wenger's side had the perfect opportunity to leapfrog their rivals back to the summit of the Premier League this evening - but instead, are left scratching their heads at what could've been.
Something that typifies their respective title charges of recent seasons, and how they've failed to sustain a proper challenge since last lifting the title itself, a decade ago.
Costa haunts Gunners once more
Diego Costa, who passed a late fitness test to start today, broke the deadlock with a well-taken strike at the near post in the 23rd minute, after intelligent movement allowed the Spaniard to weave past three Arsenal markers and fire home from Branislav Ivanovic's delivery in the area.
Five minutes before, the hosts were down to ten men. Willian slipped an excellent through ball into a pocket of space for Costa to drive forward, and Per Mertesacker made a rash decision to slide in late - hauling the forward down, and referee Mark Clattenburg adjudged the big German to have been the last line of defence in-front of Petr Čech, sending him off for an early shower.
Mertesacker's dismissal pivotal
Wenger made the decision to replace Olivier Giroud with Gabriel Paulista to compensate for Mertesacker's costly dismissal, and it proved an interesting decision - as the Gunners struggled for creativity in the final third. Whenever they found themselves in promising situations, it seemed more than a coincidence that Mathieu Flamini, of all players, was taking efforts on-goal.
A win would have boosted morale after successive away draws against Liverpool and Stoke, but the hosts lacked potency and the clinical touch in-front of goal.
Captain for the day, Theo Walcott, epitomised the hosts' frustrations. Failing to utilise his pace effectively, he was unable to get into enough attacking positions and seemed one step behind when teammates were in possession on the break.
Ivanovic's glancing header was thwarted by a goal-line clearance courtesy of Nacho Monreal; one of Arsenal's best performers on an otherwise frustrating afternoon.
Sánchez returns - an integral part of their title charge
Alexis Sánchez made his long-awaited return as a replacement, 56 minutes in, coming on for Joel Campbell. The overall tempo was increased in the Chilean's presence, which raised a question. Why didn't he start? Having missed two months with a hamstring injury, the world-class forward looked slightly rusty at times in the early minutes after being introduced, but once he got going, was effective in attack and performed tirelessly to help defensively out-of-possession.
A constant nuisance in midfield, both John Obi Mikel and Nemanja Matic picked up yellow cards after struggling to deal with just how sharp he was, once he got into the swing of things.
Čech did his best to keep his team in with a chance of snatching a point at least - but a goalmouth scramble and a few half-chances were not enough to gift the Gunners an encouraging result.