Costa is a fine player who is having an excellent season. His toughness, work ethic and finishing ability are outstanding.
Yet such is Chelsea’s financial power and history of success this century, they would simply go and buy another top-class centre-forward, such as Alvaro Morata of Real Madrid.
They are in a better position than Arsenal would be if they lost Alexis Sanchez. Arsenal could not attract a centre-forward of similar calibre. Chelsea could.
Eden Hazard is the player they really need to keep. Is there another player with those characteristics who they could expect to sign?
I see only Lionel Messi, Gareth Bale and Neymar – and I don’t see any of those three leaving Spanish football to move to Chelsea.
Both Costa and Hazard are likely to have to play key roles if Chelsea are to move 10 points clear at the top again.
While Antonio Conte’s team are strong favourites tonight, I sense West Ham are starting to settle into the London Stadium a little more now.
They have been through their horrible spell, when they suffered poor form, a long injury list and the circus surrounding Dimitri Payet, who returned to Marseille in the January transfer window.
They have lost only one of their last six league matches and I am pleased they are improving, as l like the way they try to play.
Slaven Bilic’s approach to the job is refreshing and I am a big fan of Manuel Lanzini’s creative qualities, though they have to think about their options in attack as they can look a little lightweight without Andy Carroll.
People have given West Ham a bit of leeway, because of the move to the new ground. Next season is when they will really be judged.