The Foxes were forced to a 1-1 draw by David Moyes' men at the London Stadium in the Friday Night encounter.
Marc Albrighton had given the visitors an early lead before Senegal international Cheikhou Kouyate's header on the stroke of half-time saw the two sides share the spoils.
However, Puel disclosed that Mahrez, making his 12th start in 13 league games played this campaign, was used as a bait - in the 70th minute - for their struggles against a more physical West Ham in the second half.
Left-back Ben Chilwell was drafted in place of the Algeria international who appeared unhappy while making his way out for the fifth time in the league this season.
And while the gaffer admitted to the forward’s disappointment, he was quick to play down his reaction.
"When a player leaves the game they are disappointed - it's not too important," Puel told Sky Sports.
"It was hard to find Mahrez in the second half. We tried to play on the counter attacking with Demari Gray and Vardy against this team as they were playing with long kicks and winning the second balls. But it was not possible to find them in the second half."
The former Southampton coach rued his side's inability to take advantage of West Ham's less assured performance in the opening 45 minutes which saw them continue a three-game winless run.
"We had to kill the game in the first half," he said.
"With the goal before half-time West Ham took confidence.
"They were aggressive as was the atmosphere inside the stadium. It was important then to keep this result. We couldn't find Mahrez or Vardy in space and that was a disappointment. It was difficult in the second half. But our first half delighted me for the future. We put together good moves but we couldn't find a second goal."
The Sarcelles-born player has scored two goals in 13 league games for the King Power Stadium outfit this season.