Heung-min Son admits the past season wasn't good enough at Tottenham.
Spurs finished outside the European places and also saw manager Antonio Conte depart in April.
Son said, "Just returned to Korea after finishing the season.
"Took time to come back and reflect on last season. It's a shame that I wasn't good enough, as a team, as well as the season I thought and expected.
"But I would like to say thank you to all the fans who have sent me so much support in this difficult season. Thank you very much to each and every one of the fans who have been supporting me day and night in Korea, who came to the stadium directly and online to support me this season. I promise you that I will recharge well as I was lacking and come back next season with a better and stronger look."