LONDON :Arsenal defeated London rivals Chelsea 1-0 for their first win in four Premier League games on Sunday as a headed goal by stand-in striker Mikel Merino boosted their faint hopes of catching up with runaway leaders Liverpool. Merino scored in the 20th minute when he stooped to flick his looping header over Robert Sanchez in the Chelsea goal after a Martin Odegaard corner. The Spanish midfielder, who has led Arsenal's attack in the absence of injured colleagues in recent weeks, came close