UK exhibit marks 75th birthday of football icon Pele
Costa managed to avoid a red card in last weekend's clash with Arsenal despite numerous on-field run-ins.
He was later charged by the FA and retrospectively suspended for lashing out at Gunners defender Laurent Koscielny.
Blues boss Jose Mourinho was left fuming at the decision and insists the club are hurting deeply.
However, Pele, regarded as one of the world's greatest ever players, had little sympathy.
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Pele is currently on London to attend an art exhibition titled 'Pele: Art, Life, Football'
"It is not a good message for children," he said.
"He didn’t get a red card, but he was charged. It was dirty.
"Unfortunately so many things like this happen on the pitch and this is not good. That’s clear. It is not good for football."
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The Brazil legend said Diego Costa's antics against Arsenal were dirty
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Despite his outburst, the 74-year-old did back the Spaniard to bounce back, insisting all players should be given a second chance.
"I don’t think he always used to play like that," Pele added.
"It was one mistake. Everybody can make a mistake. It is not good for football or good for him. But it was one mistake.
"There’s always been bad players and good players. It’s always been like that. But today we have more information and we get it quicker.
"Of course, what happens today, in life, used to happen years ago, but we didn’t have the information, and it’s the same in sport."