Arsenal bounced back from Erik Lamela's stunning Rabona strike to open the scoring in the north London derby to beat Tottenham 2-1 on Sunday, as Kelechi Iheanacho's hat-trick moved Leicester into second in the Premier League with a 5-0 thrashing of managerless Sheffield United.
Spurs also lost Son Heung-min to a hamstring injury on a costly afternoon for their hopes of a top-four finish, while Lamela went from hero to villain for the visitors with a needless second-half red card.Arsenal's afternoon did not start well with captain Pierre-Emerick Aubameyang dropped to the bench for a breach of discipline, reportedly after turning up late for the squad's pre-match meeting.
Lamela was introduced to replace Son early on and the Argentine opened the scoring in sensational style against the run of play as he wrapped his left foot around his right to fire into the bottom corner.
Emile Smith Rowe and Cedric Soares hit the woodwork either side of Lamela's strike but the hosts finally got their reward for a dominant first-half performance when Martin Odegaard's shot deflected in off Toby Alderweireld for his first Premier League goal.
"I think we played really bad in the first-half," said Spurs boss Jose Mourinho. "The 1-1 was not a fair reflection of the first-half. We were poor, defending bad, no intensity, no pressing, some important players hiding."
Alexandre Lacazette captained the Gunners in Aubameyang's absence and also took the Gabon international's duties from the penalty spot after the French striker was brought down by Davinson Sanchez inside the area.
Lacazette sent his international teammate Hugo Lloris the wrong way from the spot to claim a much-needed win to keep Arsenal's slim hopes of finishing in the top four alive.Arteta's side are now 10 points behind fourth-placed Chelsea with a game in hand, while Spurs remain six points behind the Blues in seventh.
Lamela was given his marching orders 15 minutes from time for a second bookable offence.
Despite their numerical disadvantage, though, Tottenham's best spell came with 10 men as Harry Kane had a goal ruled out for offside before the England captain hit the post and Sanchez's follow-up effort was cleared off the line by Gabriel Magalhaes.
"The last 10 minutes was the worst we've played," said Arteta. "We could not manage the game, we could not manage the tension.
"You have to see out the game in a more comfortable position."
- Foxes on the hunt -
Leicester showed no mercy to bottom-of-the-table United in the visitors' first match since Chris Wilder's departure on Saturday.
Wilder, who led United from third-tier League One to the Premier League, left by mutual consent after several days of speculation about his future.
The Blades, managed by interim boss Paul Heckingbottom, look destined for relegation, 14 points from safety with only nine games left.
Nigerian striker Iheanacho opened the floodgates in the 38th minute at the King Power Stadium with a close-range finish from Jamie Vardy's pass after a flowing move.
Iheanacho's third goal in his last three games was followed by Ayoze Perez's fine strike from the edge of the area in the 64th minute.
Vardy was the provider again for Iheanacho's second before the former Manchester City man completed his treble with a 25-yard blast past Aaron Ramsdale.
Ethan Ampadu's own goal from Vardy's effort in the 80th minute sealed the rout for Brendan Rodgers' side, who now enjoy an eight-point cushion over fifth-placed West Ham.
Manchester United can move back into second when they the Hammers later at Old Trafford.
In the battle to beat the drop, Brighton edged three points clear of third-bottom Fulham with a game in hand by winning a frenetic south-coast derby 2-1 over Southampton thanks to goals from Lewis Dunk and Leandro Trossard.