And the Arsenal boss revealed he would have tried to sign the Brazil-born Spain star had he known he was available.
Costa tormented Wenger’s Arsenal last season, winding up Gabriel so much a year ago at Stamford Bridge that the centre-back was sent off for aiming a kick at him as the Blues won 2-0. The red card was later rescinded.
At the Emirates in January, Per Mertesacker was red-carded in the 18th minute for hauling down Costa as he raced through on goal and five minutes later the fiery Spaniard grabbed the only goal of the game.
Today Chelsea are in north London again, with Wenger fearing that Costa, 27 – who has scored seven times already this season for club and country – could be even harder to handle.
“Of course, I like him as a player,” said Wenger. “I like the qualities of the player. All the rest around is not needed.
“He’s a very strong player. He looks since the start of the season to have cleaned up his act, that he behaves more focused on the game and that makes him more dangerous.”