The Spain international’s future has been a source of relentless speculation over the past season despite Costa playing a large part in Chelsea’s title-winning season.
The west London side won the Premier League crown with two games to spare after the Blues finished seven points clear of Tottenham Hotspur in the title race.
Costa scored 20 times in 35 games in the Premier League last season to win his second top-flight title in England since a big-money move from Atletico Madrid in 2014.
Chelsea have been heavily linked with a move to sign re-sign Romelu Lukaku from Everton in the summer transfer window.
Speaking to ESPN FC about Costa’s prospects at Stamford Bridge beyond the summer, Serie A expert Marcotti said: “It’s pretty straightforward.
“Conte has told him he’s not part of his plans and he can look elsewhere.”
Chelsea lost 2-1 to bitter rivals Arsenal in the FA Cup final.
Costa moved to Chelsea in a £32m deal from La Liga giants Atletico Madrid in the 2014 summer transfer window.
The Spanish forward has won two Premier League titles and the EFL Cup during his three-season stay at Stamford Bridge.
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