After throwing away a three-goal lead against Liverpool in the Champions League, Barca's disappointing end to the season took another turn for the worse as they were beaten 2-1 in Seville.
Denied a domestic double and a record fifth Copa del Rey triumph, the spotlight will again turn on Valverde and his future as Barcelona coach, but Bartomeu backed a coach also offered support on Friday by star player Lionel Messi.
"I've always said that Ernesto has a contract for the next season, he's the coach.
"Today I think we have to say that I do not think this defeat is the coach's fault."
Asked if the fans can expect changes this summer, Bartomeu said: "Now is not the time to explain what will happen.
"Today is just to thank the fans for their support of the team and to tell them that the season ends with a title, a league that was also very important for the club.
"This cup was not to be but we keep going and there are always changes to be made in the future. It is not the time to say it now."
Barcelona won La Liga at a canter, 11 points ahead of Atletico Madrid and 19 clear of third-placed Real. They were chasing the treble but after Saturday's loss to Valencia and the traumatic collapse at Anfield, the season ends in disappointment.
"It is not a failure," Bartomeu said. "It is not remarkable or excellent but it is a very good season because winning the league is always the goal we have.
"We fought in the final of the cup, we have reached the semi-finals of the Champions League. We always try to reach the end of the season with chances to win titles and, in the end, we lost two games."