Diego Costa all smiles with friends after Chelsea's 2-1 win over Watford

Chelsea striker Diego Costa

Diego Costa relaxed with his friends on Saturday night after the Chelsea striker scored the winner in a 2-1 victory at Watford.

The Spain international has made an impressive start to the Premier League season after scoring in back-to-back London derbies.

Costa netted an 89th-minute winner in Chelsea's 2-1 victory over West Ham United at Stamford Bridge last week.

The 27-year-old secured three points for Antonio Conte's side with three minutes remaining at Vicarage Road on Saturday evening.

And it was no surprise that the Spanish centre-forward was in good form with his friends as he wound down after the London derby.

Costa posted the above photo on his Instagram page and wrote the following caption:

"strong partnership @jaircosta19 and @jhenrique84 !!!

The Spain international moved to Chelsea in a £32m deal from La Liga outfit Atletico Madrid in 2014.

Costa won his first Premier League title in 2015 as he scored 20 times in 27 Premier League appearances.

The west London side will host promoted side Burnley at Stamford Bridge next Saturday afternoon.