Chelsea have had the upper hand for most of the first half, creating several good looks and chances and exciting passages of play, but alas, the lead is only the single goal from Marcos Alonso, his 4th of the season. Most chances, including the goal, have come from some terrific wing-play from Pedro, Hazard, Moses, and Alonso, while Matić and Kanté have controlled the middle.
Chelsea have also come very, very close to hurting Arsenal on the break, but Costa's dallying on the ball destroyed one such great opportunity while Mustafi made a terrific interception on another. The theme of Chelsea getting opportunities on the break but often wasting them continues.
Arsenal looked dangerous early, with terrific high pressure as Chelsea insisted on playing out from the back, and at times towards the end of the half. Courtois was also called into action on a header from Gabriel (a replacement for Bellerin who was concussed in the challenge with Alonso on the goal) and late in the half from Ozil after Matic contrived to give the ball away in midfield. Chelsea were scrambling in both cases; when we've stayed under control, Arsenal have been contained well.
This might come down to whoever makes the next mistake. Chelsea have been largely mistake-free, but a little ragged at the start and at the end of the half. Need that second goal.
COME ON, CHELSEA!