Son was booked in the first half after going down in the area under a challenge from Harry Maguire, becoming the fourth Spurs player to be yellow-carded for simulation this season.
In the Premier League, Tottenham remain within five points of Liverpool and Manchester City after beating Leicester. Lloris made a string of excellent stops including a penalty save when Jamie Vardy took the kick with his first touch as a substitute.
Pochettino has not forgotten that incident and was incredulous in his response to Sunday's re-run.
"The problem is, I told Michael Oliver [about] the situation against Liverpool in the last minute that should have been a penalty". It is so hard. I am a person who accepts the mistakes, but today it was so clear.
In Sunday's early match, Tottenham kept alive their bid to gate-crash the Premier League title race with a 3-1 win over Leicester City, their fifth win in their last six league games.
Dortmund played on Saturday and the Argentinian believes his side are now at a massive disadvantage by having 24 hours less to recover.
"I think it's hard", he said.
"It doesn't mean we can't compete, but for me it doesn't make sense".
"I can't understand why we are playing with such a massive disadvantage". I think if you want to fight for big things, you need a little bit of luck and it was for our side, but we deserved it.
The striker had an opportunity to prove himself after being dropped by Claude Puel.
Puel opted to leave Vardy on the bench, but the former England striker came on to take Leicester's penalty after James Maddison was fouled.
Tottenham went ahead through Sanchez who scored his first goal for the London club by meeting Eriksen's whipped cross with a diving header in the 33rd minute, although Leicester's players complained he was in an offside position. "All the game we had a lot of chances".
There were many good performances in a Spurs shirt in the encounter, but the best one was from Eriksen.
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