LONDON, (Reuters) - Alexis Sanchez grabbed a 15-minute hat-trick as Arsenal shook off any hangover from their midweek League Cup defeat to thrash West Ham United 5-1 and climb to second in the Premier League on Saturday.
The visitors toyed with struggling West Ham for most of the derby at the London Stadium but did not finish them off until Sanchez's lethal second-half intervention.
The Chile international has now been involved in six of Arsenal's last eight league goals, scoring five, and he earned high praise from manager Arsene Wenger whose decision to play him as an orthodox striker is paying off handsomely.
"He has all the ingredients to be a top-class striker and he showed it again today," said Wenger as his team got back on track after drawing two of their last three league games and suffering League Cup defeat by Southampton.
"He is quick, can dribble, has a short backlift and has the killer instinct the top South American strikers seem to have."
By contrast West Ham's woes worsen by the week.
They have won only two of seven games at their new home and fans voted with their feet on Saturday, making a stampede for the exits when Arsenal went 3-0 up.
"We don't have the level of intensity that is required," said manager Slaven Bilic with his side one place above the relegation zone.
"We have to get it back as soon as possible. It's not there in training so it's impossible to have it over 90 minutes in this league."
West Ham suffered an early injury blow when defender James Collins was replaced by Alvaro Arbeloa.
That they only trailed to Mesut Ozil's 24th minute tap-in at halftime was down to Arsenal's casual finishing.
West Ham improved after the break and nearly equalised when Pedro Obiang fired wide.
Arsenal awoke from their second-half slumbers and home keeper Darren Randolph made a superb double save to deny Aaron Ramsey and Ozil but could do nothing to stop Sanchez's angled drive after 72 minutes following the Chilean's neat turn.
Sanchez threaded his second past Randolph soon after before West Ham substitute Andy Carroll marked his first appearance since August by heading in the rebound after the otherwise-quiet Dimitri Payet hit the bar.
Alex Oxlade-Chamberlain curled in Arsenal's fourth goal before Sanchez completed his hat-trick with a clever dink over Randolph after racing through alone.
Reporting by Martyn Herman; Editing by Tony Jimenez