The German watched the 1-0 win over Saudi Arabia's Al Hilal at home in London, having also missed Saturday's FA Cup victory over Plymouth.
But, after returning a negative test, Tuchel took a last-minute flight to join up with his squad on Friday.
Assistant coach Zsolt Low had been standing in for the Blues boss.
Low had earlier said goalkeeper Edouard Mendy is "absolutely ready to play" in the final after helping Senegal win the Africa Cup of Nations.
Low says he will speak to Tuchel before a decision is made on who will start in goal.
"We will talk to Thomas about it," he said.
"The final decision will be some hours before the game but if we decide for one or the other, the one on the bench has nothing to be worried or sad about.
"Both goalkeepers had a big performance in the last weeks and this is why it's a question just for this game."
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