The winning goal came two minutes after Hazard was replaced with Pedro, and Courtois does not get the change.
Free to leave at the end of next season, Chelsea must weigh-up whether to cash-in on Courtois this summer if he refuses to sign a new contract to risk losing him for nothing at the end of the next campaign.
Speaking in an interview with Belgian outlet Play Sports, Courtois said: "I have no explanation for the substitution of Hazard".
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The youngster in fact has 15 appearances already under his belt this season and, playing alongside the Serbian, has managed to impress him.
His form for City over the past few years makes Chelsea's decision to sell him look all the more ridiculous - even Hazard knows they made a huge mistake.
Antonio Conte's menlost to Manchester United in their last league fixture, and now face runaway Premier League leaders Manchester City in their next fixture, before an elimination game against Barcelona in the Champions League.
Speaking after the defeat at Old Trafford, Conte suggested that Hazard had failed to maintain his high standards in the second half and that his withdrawal was merely a tactical decision.
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She was well known to have the ear of the president, who never publicly voiced even the slightest criticism of her. Hicks also bested Mike Dubke, who bid farewell before reaching the 90-day mark.
The former Atletico Madrid stopper is open to extending his stay with Chelsea, who are also hoping to tie down his compatriot Eden Hazard, a player also of interest to Real Madrid. "He can always bring something extra".
"No Hazard [is not injured], no", he told a news conference. "The second half he started the same way, but when I see a player is a bit exhausted, my task is to find a different solution".
Thibaut Courtois' agent has denied reports that PSG had held a meeting with the Chelsea goalkeeper's father. "If you do not do the small things well in top matches, you lose, which is what happened", he added.
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What needs to be discussed is reducing gun ownership in US. "He surprised me", Democratic Senator Chris Murphy later told AFP. While there were few open displays of grief, many students looked sombre, speaking in hushed tones with their eyes downcast.