Arsenal manager Arsene Wenger praised his side's discipline after a superb 2-0 win away to Premier League champions Manchester City on Sunday left leaders Chelsea five points clear at the top of the table.
Earlier in the day, West Ham beat relegation-threatened Hull City 3-0 to move up to seventh.
In Manchester, Santi Cazorla produced a midfield masterclass, scoring a penalty in the 24th minute and then providing the free-kick from which France striker Olivier Giroud headed the Gunners into a 2-0 lead midway through the second half.
The result meant Arsenal's London rivals Chelsea, who thrashed Swansea 5-0 on Saturday, remained five points clear of second-placed City with 16 league games of the season remaining.
Arsenal have struggled against fellow leading English clubs in recent campaigns - last season's trip to City saw them crushed 6-3.
But they have now closed to within a point of fourth-placed Manchester United and this performance could yet inspire Wenger's side to aim for more than just another top-four finish, although they are still 13 points behind Chelsea.
"I felt that we were well-disciplined, well-organised, had a good solidarity and overall we kept a good control of the game," Wenger told Sky Sports.
"We looked in control away from home and we finally got a big win in a big game away from home," veteran manager Wenger, in charge of Arsenal since September 1996, said.
Turning to Spain international Cazorla, Wenger added: "Santi Cazorla has been superb for a while now but today he was maybe even more influential.
"When you give him the ball you always have a chance to relieve pressure," explained the Frenchman, who last led Arsenal to the Premier League title in 2004.
Pellegrini's penalty anguish
This loss was City's first defeat in 15 games and manager Manuel Pellegrini was unhappy with the award of the penalty that broke the deadlock at the Etihad after City captain Vincent Kompany stepped across Nacho Monreal's path, making contact with the Spaniard.
"There are two principal reasons (why we lost): one was the penalty, which changed the game.
"I don't think it was a penalty, but it was unnecessary (for Kompany) to do it," the Chilean added.
"The movement of Kompany allows him (Monreal) to dive. I am not saying it was a bad mistake of the referee (Mike Dean). The penalty changed the game, but it was not the reason we lost.
"We were not creative - we didn't have the ideas to cause damage in their defence.
"Of course, I always give credit to the team that wins the game. Arsenal played very concentrated.
"We still have to play against Chelsea so it will be a very decisive game. We will try to win that game to close that gap again."
Hammers striker Andy Carroll said his side were eyeing European football after he scored the opener against Hull.
Second-half goals from Carroll, Morgan Amalfitano and Stewart Downing secured all three points for the east London club following a run of four games without a win.
Asked if West Ham could qualify for Europe, England striker Carroll said: "There's a belief in the dressing room, I don't see why not."
Hull were punished for failing to take their chances and this defeat left them in the relegation zone.
Frustrated Hull manager Steve Bruce said: "The way we played in the first half delighted all of us connected with Hull but in my experience you have to score.
"For all the good work we did, it unravelled really. You can't let them off the hook like that."