Liverpool moved one point clear at the top of the Premier League after being forced to settle for a 0-0 draw at injury-ravaged Manchester United on Sunday.
Jurgen Klopp's side climbed above Manchester City into pole position, but left Old Trafford frustrated that they failed to go three points clear after struggling to break down a United team hit by three key injuries.
Liverpool, chasing a first English title since 1990, had few chances to beat their bitter rivals despite United losing Juan Mata, Ander Herrera and Jesse Lingard before the interval.
The Reds now have 11 league games remaining, the same number as second placed City, who are in League Cup final action against Chelsea on Sunday.
At the same time, Arsenal cruised to victory over a disjointed Southampton thanks to two first-half goals from Alexandre Lacazette and Henrikh Mkhitaryan at the Emirates on Sunday, taking them back into the top four in the Premier League.
Arsenal took the lead in the sixth minute in bizarre circumstances, Lacazette neatly back-heeling in a pass from Mkhitaryan while the rest of the team were still appealing for a penalty after Lucas Torreira took a tumble in the box.
The home side doubled their advantage minutes later when Southampton keeper Angus Gunn, making only his second Premier League appearance, cleared the ball straight into the path of Arsenal's Alex Iwobi.
The result moves Unai Emery's side up into fourth place in the standings on 53 points after Manchester United were held to a goalless draw by Liverpool at Old Trafford.