Five talking points from the weekend's EPL

Raheem Sterling scored a second-half hat-trick as leaders Manchester City beat Watford 3-1 on Saturday while Liverpool kept the gap at one point by overcoming Burnley 4-2 on Sunday.

Arsenal beat Manchester United 2-0, lifting the Londoners into fourth place and ending Ole Gunnar Solskjaer's unbeaten domestic run as United's caretaker manager.

The following are five talking points from the weekend:

PITCH INVASIONS PART OF A GROWING PROBLEM

Manchester United defender Chris Smalling was shoved by a pitch invader at Arsenal while Aston Villa's Jack Grealish was punched in the face by another in a Championship game at Birmingham City.

Gordon Taylor, chief executive of the Professional Footballers' Association (PFA), saw a growing problem.

"We have seen an increase in such behaviour at clubs this season. It's been racist abuse, anti-Semitism and now its real fear for the safety of players," he told Sky Sports television.

Grealish went on to score the winner for Villa while Smalling said on Twitter that commenting on his attacker "would only add to the attention he craved".

But while individuals were arrested, and face court action, there is plenty of debate about how to prevent such incidents, the risk of a more serious attack and the potential ramifications.

"What next...a knife?," declared the back page of the Sun tabloids.

Should there be a points deduction for a side whose supporter assaults a player? Or would that merely encourage some to pretend to be fans of another club in the hope of deliberately triggering a sanction? Ground closures?

What happens if a key player, such as Grealish, has to leave the field of play due to an injury sustained in an assault by a pitch invader? Or reacts, and is then shown a red card?

ARSENAL TO FINISH ABOVE TOTTENHAM?

Arsenal's home win sent them fourth and just a point behind North London rivals Tottenham Hotspur, who lost 2-1 at Southampton.

So have Spurs run out of steam after looking sure to finish at least third?

On paper, Arsenal have the easier run-in with only clubs below them to come while Tottenham still have to play Manchester City and Liverpool and are still in the Champions League.

The Gunners have not lost at home since the opening day of the season, and won their last nine at the Emirates, with manager Unai Emery winning plaudits for his bold tactics.

SETBACK FOR SOLSKJAER

"Maybe a backlash from Wednesday night," said Solskjaer after Sunday brought a first domestic defeat to his remarkable run as Manchester United caretaker.

When you have pulled off the sort of Champions League comeback United achieved against Paris St Germain to reach the quarter-finals, the Norwegian can afford a shrug.

The defeat should certainly not dent the momentum building behind Solskjaer getting the job permanently.

"Solskjaer has connected the club, the results have been incredible and there was always going to be a defeat. But it's not been a defeat that's embarrassing," said former United team mate Gary Neville.

VAR AND OFFSIDE RULE

Burnley manager Sean Dyche has been around football long enough to have seen most things but he admitted to being "completely discombobulated" by current interpretation of the offside rule.

"I just liked it in the old days when they would just be offside and everyone would go ‘right they are offside’. It has just got so technical now," he told Reuters. "I marvel at when they (officials) get it right because I think it is just so confusing."

Sterling's first goal against Watford at the Etihad triggered controversy, with referee Paul Tierney changing his mind about an offside call after a discussion with his assistant.

The decision appeared to be over-ruled because Watford defender Daryl Janmaat played the ball against Sterling, who appeared offside, as the City striker aimed for goal.

Another good reason, as Manchester City manager Pep Guardiola said, for the introduction of the video assistant referee (VAR).

NO LOSS OF BOTTLE AT LIVERPOOL

Some people thought Liverpool had lost their bottle after recent results dropped them go from seven points clear in January to four behind Manchester City on Saturday, but they showed plenty of fighting spirit on Sunday.

Burnley can be a tricky side and Liverpool were behind after six minutes on a gusty and wet afternoon at Anfield, but battled back to get the job done.

"Nobody gets rid of us if we play as we played today, because we had the perfect mixture of fighting the opponent, fighting the circumstances and playing football," said Liverpool manager Juergen Klopp.

"We have no problem with confidence."