The Catalan outfit failed to pick up a major trophy this season – conceding the league title to Atletico Madrid, in addition to exiting to the same opponents in the quarter-finals of the Champions League and losing the final of the Copa del Rey to Real Madrid.
However, the 26-year-old has insisted that the former La Liga champions will respond in the 2014-15 campaign.
"Things didn't turn out as we had expected. It was a tough year personally and collectively," he wrote on social networking site Tencent Weibo.
"Despite this, we had the chance to achieve an objective in the last game and we were unable to take advantage of it. I can only say sorry to all the Barcelona fans and promise them that next year we'll meet the demands of this club again."
It has been reported that Messi will not officially sign his new deal with Barca until the completion of the World Cup this summer.