MANCHESTER -- It was when Manchester United defeated Arsenal in a seismic FA Cup semifinal in April 1999 that Sir Alex Ferguson's team started to believe they could achieve the unthinkable by doing the Treble. Manchester City's rampant 4-1 victory against the same opponents on Wednesday has now done the same for Pep Guardiola's side.

The Treble is on. City are 11 games from greatness and from erasing the word "unique" from United's claim to be the only English club to win the Premier League, FA Cup and Champions League in the same season.

United have the chance to halt City's march and ensure that Old Trafford remains the only English ground to house those three trophies at the same time, by beating their neighbours in the FA Cup final on June 3.

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But City are now displaying such ominous form that the Treble has gone from being impossible to improbable to seemingly inevitable. Arsenal could have de-railed City's charge completely by winning at the Etihad, but they never came close.

By beating Mikel Arteta's team -- who have led the Premier League table for 28 matchdays compared to City's four -- City are now in full control of the title race. They remain in second position, but are only two points behind the Gunners having played two games fewer. Win both matches and they will be four points clear, but they will even claim top spot with two draws due to their vastly superior goal difference.

"The next three games are really, really important," Guardiola said. "Game by game and we will see what happens. The reality today, it's sounds naive, but we are behind Arsenal on the league table."

All true, but the league title is now City's to lose. Yet winning the Premier League for a third successive season is now just one strand of a bigger objective. It is all about the Treble. Even if City win the league and the club's first Champions League, this season will go down as a story of what might have been if they don't win all three competitions they are still alive in.

That might sound ridiculous when you consider that City have tried and failed so many times to get their hands on the European Cup, but if they lose to United in the FA Cup final and win the Champions League in Istanbul a week later, Guardiola's team won't be Treble winners, unlike Ferguson's greatest group of players in 1999.

Success beckons for Guardiola's team in the Premier League after this victory, but to achieve greatness, they have to win the Treble.

Of those 11 games they have still play -- seven in the league, one in the FA Cup and three in the Champions League (if they get to the final) -- the reality is that only United at Wembley and Real Madrid in the two-legged Champions League semifinal stand between them and the Treble.

City utterly dismantled Arsenal in this game with Kevin De Bruyne scoring twice in a majestic performance and Erling Haaland netting his 33rd league goal of the season with the last kick of the game. A John Stones header on the stroke of half-time, initially ruled out for offside, had made it 2-0 after the intervention of VAR.

Arsenal, so good this season, were blown away. All of a sudden, they looked like what they have been for the past decade -- a team fighting for a place in the top six rather than a title challenger -- and City ruthlessly dispatched them with their superior quality and experience. Rob Holding's late goal for the Gunners was no consolation whatsoever.

But while City still have plenty of games to play, nobody would back them to drop points in their final seven league games against opponents much less impressive than Arsenal.

They are unbeaten in 17 games in all competitions and their remaining league fixtures see them play Fulham (a), West Ham United (h), Leeds United (h), Everton (a), Chelsea (h), Brighton (a) and Brentford (a).

Are they really going to drop more than four points against those opponents? And if they do, Arsenal will have to win all five of their remaining league games. The screw is tightening every week in the Premier League.

In the Champions League, Madrid are formidable opponents and the true test of City's Treble chase. But if they overcome Carlo Ancelotti's team, it really is difficult to envisage Internazionale or AC Milan beating City in Istanbul.

So maybe it all comes down to the FA Cup final and United. City have made history under Guardiola by achieving a domestic Treble and becoming the only team to amass 100 points in a Premier League season, but only United have done the real Treble.

Maybe not for much longer. That distinction might just be 11 games from being matched by City.