Tuchel claimed Lukaku, who was introduced at half-time at the London Stadium for the injured Kai Havertz, should not have been used as the Belgian remains short of the requisite match fitness to compete for long periods in the Premier League.
"It's my fault," he said. "I don't think he is ready for 45 minutes physically but still we decided to bring him on for his height because we lost Kai.
"Kai had a crucial role in defending set-pieces, which is a huge threat from West Ham, so this is on me.
"I took the decision so it's my responsibility."
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