Lavia was replaced by Malo Gusto at the interval during the Blues’s dramatic 4-3 win over their London rivals.
The 20-year-old had earlier been left with a nasty cut by an elbow from Spurs midfielder Dejan Kulusevski, which went unpunished by referee Anthony Taylor.
Lavia shared a picture of the wound on social media soon after full-time, but Maresca says a different issue forced his withdrawal.
“Unfortunately he felt something in his hamstring in the last minutes of the first-half,” the Italian explained. “Now, he’s walking without any pain. It was a small thing.
“Since we started, I don’t like to lose players for five, six, seven games in a row. Even if Romeo was playing fantastic, we tried to change because he had a problem.”
Chelsea have been cautious with Lavia’s workload this season, after he missed almost the entirety of his first campaign at Stamford Bridge through injury.
The Belgian has been left out the Blues’s squad for the Conference League group stage, meaning he could not feature against Astana on Thursday night even if fit.
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