(Reuters) - Borussia Dortmund striker Sebastian Haller has returned to training after undergoing multiple surgeries and chemotherapy for a testicular tumor discovered in July. 

"Happy New Year everyone! It's a great start for me because it means getting back on the field," the 28-year-old Ivory Coast international wrote on Twitter, posting pictures of himself training in the gym.

 "2022 was not the easiest year, but it prepared me for all the new challenges that 2023 will bring," he added.

 Dortmund signed Haller for an initial fee of 31 million euros ($33.02 million) during the summer transfer window, after the striker scored 34 goals last season with Dutch champions Ajax Amsterdam.

 Dortmund said Haller would be "carefully pushed" into the squad again.

 Dortmund ranks sixth in the Bundesliga, nine points behind leaders Bayern Munich.  The season will resume later this month, when Dortmund will meet Augsburg on January 22.