Just three days after Monaco claimed a crucial win at Bayer Leverkusen in the UEFA Champions League, the club from the principality were far from their best at Rennes' Stade de la Route de Lorient.
Jardim was frustrated by how his team allowed Rennes dangerman Paul-Georges Ntep to use his pace down the left and set up both goals on Saturday.
Ntep's cross in the 10th minute was turned into his own net by Monaco defender Aymen Abdennour, while the 22-year-old winger teed up Ola Toivonen nine minutes later and the Swedish striker made no mistake.
"The team were not focused enough at the start of the game and that allowed Ntep to win the match all on his own in the first half," Jardim said, according to Ligue1.com.
"We made two or three defensive errors that allowed Rennes to dictate the result. Knowing the opposition, and with the information we gave to the players, they knew that they could not afford to make such mistakes against Rennes.
"We said before the match that we mustn't allow Ntep to find himself one-on-one and we allowed him to do it."
Rennes coach Philippe Montanier was thrilled as his team moved up to fourth in Ligue 1 with 25 points, two behind third-placed Lyon and five clear of Monaco, who sit 10th.
"I am really satisfied. We handled the game well, taking the lead early on. We were not far away from winning by a greater margin, but overall we can be satisfying at doing what we intended to do," he said.
"Between the defensive aspect, winning the ball back, a better overall control of the game, the two goals and the other chances we created - because their goalkeeper made two or three saves - it was a complete performance, perhaps the most complete since the start of the season."
