Diego Costa spent the last three weeks of José Mourinho’s tenure at Chelsea voluntarily taking part in double training sessions to improve his fitness.

The Spain striker bore the brunt of anger from Chelsea fans during the 3-1 home win over Sunderland on Saturday, along with Cesc Fàbregas, as both players were booed when the teams were announced before kick-off and again after their second-half substitutions. They were also named in a banner produced by one fan, who accused them and Eden Hazard of being the “rats” who had undermined Mourinho, a phrase that the Portuguese used when complaining about leaks of his tactics in October.

Costa has struggled for form this season and had several heated conversations with Mourinho before his departure last week,