Zinedine Zidane was left furious after Sevilla were given a spot-kick for handball against Eder Militao as Madrid were held 2-2 on Sunday, meaning the LaLiga title is no longer in their own hands.
Los Blancos thought they had earned a penalty for Yassine Bounou's foul on Karim Benzema at 1-1, only for a VAR review to overturn the decision because of Militao's handball at the other end at the start of the move.
Sevilla were instead awarded a penalty and Ivan Rakitic converted from 12 yards, though Madrid did at least rescue a point in the 94th minute through a goal later credited to Eden Hazard in what is the tightest LaLiga title battle in years.
Barcelona have themselves been on the wrong end of some controversial decisions this season, with Koeman questioning why VAR is even used in the Spanish top flight after his side were denied two penalties in their loss to Madrid.
The Dutchman, who has just served a two-game ban for comments made to the fourth official during last month's shock 2-1 home loss to Granada, did not want to get involved in the drama that unfolded at Estadio Alfredo di Stefano.
"If someone is better off not talking about refereeing, it is me," he said at a news conference on Monday previewing his side's trip to Levante. "I have already said what I think, my opinion has not changed.
"If Madrid think they were harmed, that is their problem. As for VAR, I will not repeat any more."
Barcelona remain two points off leaders Atletico Madrid following Saturday's stalemate between the sides and level on points with Madrid, who are one place better off due to their superior head-to-head record over their Clasico rivals.
Barca have collected just 10 of the last 18 points available in LaLiga, after picking up 45 from the previous 51, which Koeman puts down to fatigue at the end of another grueling campaign behind closed doors.
"There are a lot of games that take their toll," the Dutchman said. "It is normal for all teams, especially those who have played in Europe and have reached cup finals this season.
"In addition, playing without an audience can also play a part. That's why many teams have dropped points at home. It's not normal for so many games to be played. The team that is physically and mentally stronger will win the title.
"We will fight until the last moment to win the league. It is not in our hands and we cannot afford to make any mistakes."
Koeman has another year to run on the contract signed when taking over as Barca boss last August, but his future will reportedly come down to whether his side finish top of the LaLiga standings or not.
However, the Dutchman remains confident he will still be in charge at Camp Nou next season regardless of results over Barca's remaining three matches.
"There is nothing to answer on my future," he said. "You don't have to look for stories that are not there. From the first day he arrived, the president has shown me his confidence. If anyone can decide, it's him.
"The future is not for me to be worried about because I've signed two years as a coach. We have agreed to talk after the season, but before then we have two weeks and three more games to go.
"I cannot win a battle with the press or people on the outside. For many periods this season they have valued me. For me, the important people are those who I work with every day and who value what we are doing."
Koeman has not lost any of his two matches against Levante as a manager, with his teams keeping a clean sheet in both previous encounters, including a 1-0 win for Barcelona in this season's reverse fixture.
However, Levante have won two of their last three meetings with Barcelona at the Ciutat de Valencia in LaLiga - one more than they had in their previous 11 home games against them in the competition.