Leicester goalkeeper Kasper Schmeichel said it was "plain and obvious" that the foul that led to Atletico Madrid's penalty in the 1-0 win in the Champions League quarter-final first leg was outside the box.
Schmeichel, who captained the Foxes at the Vicente Calderon, said on BT Sport 2: "It was plain and obvious to see, it has ruined our game plan.
"It is a decision that is tough to take when it is so clear and obvious. We should have had something from this but we have to accept it.
"We made a challenge outside of the box. They might have scored from that free-kick but obviously there is a much better chance of scoring from the penalty. But it was never a penalty."
Boss Craig Shakespeare was in agreement and said Eriksson should only have made the decision if he was sure.
"It's disappointing, it's a key moment in the game, it is a really disappointing decision by the referee," he added. "He has to get that one right, he can't guess on those things. It's a definite free-kick but it's out of the box.
"It's the key decisions you want correct."
Despite their loss, Leicester's hopes of making the semi-finals are still alive, though they will need a repeat of their last-16 antics, where they overturned a one-goal deficit against Sevilla in their home leg.
Shakespeare is confident they will have a chance on home soil.
"I think 1-0, we would have taken that before the game," the boss added. "We came to try and get the away goal but we have seen what a top team Atletico Madrid are.
"We have got a good record at the King Power and the tie is still alive."
Even though they lost, midfielder Andy King reckons it is still job done.
"To come here and still be in the game was the main objective of tonight," he said. "We can take them back to ours like we did in the last round and overturn the deficit.
"We can take them back to the King Power and try and make a night of it. We are strong at home and I am sure we can cause them problems back there."