The 2-1 defeat meant Barcelona ended the season with just one major piece of silverware, the league title, when a treble looked all but assured a six weeks ago.
But Bartomeu had words of support for his manager despite this latest setback.
‘This defeat was not the fault of the coach,’ he said.
‘We had many chances to win the game, but the ball just would not go in the net.
‘I would say that the season has been very good, without being excellent.
‘We have lost a few key games here in Spain and at Anfield, and that has cost us two titles.’
Pushed specifically on the future of Valverde at the Nou Camp, Bartomeu said:
‘Valverde has a contract here and he is the coach of the team.
‘However, now is not the time to speak about these things, but we are planning for next season.’
Valverde agreed a one-year contract extension, taking him to the end of the 2019-20 season, back in February.
But although Barcelona defended their league title by a comfortable margin, their defeat in the Champions League – and subsequently the Copa del Rey final – has placed doubts on his future.
Barca fell two goals down to Valencia in the first-half at the Benito Villamarin in Seville thanks to goals by Kevin Gameiro and Rodrigo. Lionel Messi pulled a goal back but they were unable to get back into the match.