This step was big for us, a big win. When you play and win against United at home in the way that we did. "It was a great performance, my players showed commitment, workrate for an three important points", the Italian told BBC Sport.
"For sure this moment is a really good moment for us as we are so close to reaching a fantastic target for us". They dominated the game right from the start.
Costa scored his 20th league goal of the season, converting a pass from the excellent Cesc Fabregas, and Alonso netted from a similar position before half-time before Nemanja Matic's second-half goal.
Premier League leaders Chelsea are on the verge of sealing the title after beating Middlesbrough 3-0 to condemn the North East outfit to relegation.More news: Joanna Jedrzejczyk on Jessica Andrade and Aiming for UFC Flyweight Title
Conte's wife Elisabetta Muscarello was also in the stands at Stamford Bridge.
"They will give us a very hard game there and we have to stay focused like we were at Everton and against Middlesbrough". For this reason I felt in my heart to go and clap these fans and also to say good luck for next season to every single player.
The 30-year-old's impressive total for 2016/17 ranks him fourth in the division, despite being a back-up option for Antonio Conte for much of the season. "It's great for me, great for the players and for the club".
Boro are the second team to be relegated from the English Premier League to the Sky Bet Championship this season, following Sunderland.More news: Sharapova more disappointed to lose early than to detractor
West Brom have beaten Chelsea in three of their last five league meetings at The Hawthorns.
'I think that when you suffer, you become stronger and then you are ready to face every situation - above all, problematic situations during games.
"We all know it's a Premier League football club in everything - the supporters, the stadium, the training ground, the infrastructure is all there - so the most important thing is to finish the season strongly with two more games to go".
Arsenal manager Arsene Wenger feels that teams battling in Europe and domestically will find it hard to win the coveted English Premier League (EPL) title.More news: British PM May's Conservatives open up record lead: ICM poll