Hull looked bright after the restart, with Everton lacking the zip and guile that was present in the opening stages, though Lukaku went close with a rasping strike.
Lukaku scored twice in Everton's 4-0 win over Hull City.
"The fans love Rom and everyone loves Rom. Everybody loves Rom", Koeman said of Lukaku, who has just over two years remaining on his current deal. If he gets that space he will punish the opposition and that's one of his big qualities.
"We didn't deserve this decision on 70 minutes to make us play with 10 players".
"Every day Everton is trying to get the best and strongest team we can have".
Dominic Calvert-Lewin tapped home from close range to put the Toffees ahead after connecting with Tom Davies' low cross - his first Premier League goal.
"We kept the momentum".
United Kingdom prime minister doesn't back second Scottish independence vote
She said Britain stands on the threshold of one of the most significant moments the country has known for many years. Imagine if the European Union had interfered in the UK Government's plans for the UK's EU referendum a year ago .
"I am a little bit anxious he will be out for several weeks but we need to wait for the scan to know what happened", added Koeman, who felt Huddleston's dismissal was "harsh".
Huddlestone was dismissed in the 73rd minute when referee Paul Tierney ruled his lunge on Lukaku was worthy of a straight red card.
"But I think everybody needs to understand ambitions, and his situation I tried to explain - he's a professional player and his commitment maybe looks different because of two or three quotes in the press but he is young and we can see these things".
"We now have the opportunity in two weeks to play Liverpool and Manchester United".
However, a move for Lukaku is not dependent on Costa leaving and Chelsea have marinated that they want their Brazlian-born centre forward to stay, with the prospect of a new deal open to him if he commits beyond the summer.
"We didn't deserve this result and we didn't deserve what happened", Silva said. We didn't deserve this.