The Barcelona president says that he was not surprised by the Argentine's two-goal display at Sevilla but that talks over a new deal for the 26-year-old are not imminent
Along with the rest of his team-mates, Messi performed poorly in February 1's 3-2 defeat at home to Valencia, leading former Barca assistant Angel Cappa to claim that the Argentine had lost his passion for the game.
However, the 26-year-old hit back in some style with two great goals in wet and windy conditions on Sunday as Barcelona beat Sevilla 4-1 at the Estadio Ramon Sanchez Pizjuan.
"We were not worried," Bartomeu told reporters of Messi. "Everyone is entitled to their opinion [but] we are closer to him than the people who are writing or talking.
"He makes the difference and he showed that [on Sunday] in very difficult conditions."
However, the new president claims that there are no talks planned at the moment to improve the Argentine's current contract at the Catalan club.
"Leo has a contract," he remarked. "He is the best player in the world and we want him to be the highest-paid player in the world. When the moment is right, we will look at it [his renewal].
"At the moment, however, we are focused on the [three] competitions, so it's not the time to talk about that."
Also asked about a possible new contract for coach Gerardo Martino, Bartomeu gave a similar response.
"He is doing a magnificent job," the president replied. "Now is not the time to negotiate but we are delighted with his work."
Barca take a 2-0 lead to Real Sociedad on Wednesday as the two sides meet in the second leg of their Copa del Rey semi-final, while the Catalans face Manchester City in the last 16 of the Champions League later in February and currently lead La Liga on goal difference from both Real Madrid and Atletico.