The way Chelsea beat Tottenham in Saturday's FA Cup semi-final showed why they are going to win the Premier League title too.
As usual, Antonio Conte's side were dogged and resilient - and the manager's game plan worked perfectly.
They were content to soak up Spurs' pressure and possession and, when they went up the other end, they took their chances brilliantly.
The Blues scored four goals against the team with the best defensive record in the top flight, so you cannot say they did not deserve their victory.Highlights: Chelsea 4-2 Tottenham
And anyone who doubted Chelsea after their defeats against Manchester United and Crystal Palace just had to watch them at Wembley to see how good they are.
This was a superb display that won a brilliant cup tie and, psychologically, could and probably should pull them across the line in the title race too.
They know they beat their closest rivals despite not having three key players for the majority of the game - Gary Cahill, who was out injured, and Eden Hazard and Diego Costa, who came off the bench with less than half an hour to play.
Conte's big gamble pays offSub Hazard fires Chelsea in front again
Conte's decision to leave Costa and, in particular, Hazard out of his starting line-up was a huge call, but it worked.
The guy he brought in for Hazard - Willian - scored twice. Then, when he brought Hazard on in the second half, he changed the game.
Hazard scored Chelsea's vital third goal and he also rolled the ball into Nemanja Matic for his fantastic strike to make it 4-2.
When you make big decisions, you want them to work in your favour, and things could not really have worked out any better for Conte on Saturday.
He has not got very much wrong in his first season in the Premier League, especially since switching to his favoured formation of three at the back at the end of September.
The double is definitely on, which would be an incredible achievement.
Kenny Dalglish (with Liverpool in 1986) and Carlo Ancelotti (with Chelsea in 2010) are the only other managers to have done it in their first season in England, and now Conte has a fantastic chance of doing the same.
Tottenham did not make their possession countMatic thunderbolt sends Chelsea to final
The two teams' benches illustrated the difference in depth between the two sides, because Chelsea's substitutes made a huge difference, and Tottenham's didn't.
It obviously helps when you have got big hitters like Hazard, Costa and Fabregas to come on like Chelsea did.
But I still think Spurs wasted a great opportunity to beat a weakened Chelsea team.
Tottenham dominated possession - they had 63% of the ball and played 544 passes to 323 by Chelsea - but I don't think they did enough with it.
They only had four shots on target, and one of them was in the 93rd minute.
Kane took his goal very well and Dele Alli's goal to make it 2-2 was a superb finish from a brilliant ball by Christian Eriksen.
The way Alli found the space inside the area was very similar to the headers he scored when Spurs beat Chelsea in the league in January but, other than that, they did not open Conte's side up often enough.
No trophy for Tottenham this timeHarry Kane has scored nine goals in his last 10 London derbies in all competitions
As much as victory will lift Chelsea, this defeat will damage Tottenham - who have now lost seven straight FA Cup semi-finals.
I don't think it affects Spurs' title hopes, because I never thought Chelsea would chuck the league away whatever happened at Wembley.
But, trophy-wise, it now looks like Mauricio Pochettino's team will not have anything to show for their season, and I think the next 12 months is going to be a crucial time for the club.
If you go through the Tottenham team, they have one of the best goalkeepers in the Premier League - if not the best - in Hugo Lloris, and they certainly have the best defender in Toby Alderweireld.
Alli is one of the most sought-after young players in the world and Kane is one of the best strikers in the Premier League, and with Victor Wanyama and Mousa Dembele in midfield they have one hell of a spine.
But all that talent needs to get over the line in something, soon.
They need to win a trophy next season, otherwise I fear that their top players will look to go elsewhere to get some silverware.
Alan Shearer was speaking to Eyes On Events Sport's Chris Bevan.