Borussia Dortmund striker Sebastien Haller has returned to training after undergoing surgeries and chemotherapy to treat a testicular tumour that was discovered in July.

"Happy New Year to all! And it's off to a great start for me because it means getting back on the field," the 28-year-old Ivory Coast international wrote on Twitter, posting images of himself working out at the gym.

"2022 wasn't the easiest year but it prepared me for all the new challenges that 2023 will bring."

Bonne année à tous ! Et elle commence très bien pour moi car elle est synonyme de retour sur les terrains ! 2022 n'a pas été l'année la plus simple mais elle m'a préparée pour relever tous les nouveaux challenges que vont m'offrir 2023 ?? Hâte de tous vous revoir ?⚫️ pic.twitter.com/EwG4vBSmwf

— Sébastien Haller (@HallerSeb) January 2, 2023

German side Dortmund signed Haller for an initial fee of €31 million during the close season after the striker scored 34 goals last season for Dutch champions Ajax.

Dortmund said Haller would be "carefully introduced" back into the team.

The club are sixth in the Bundesliga, nine points behind leaders Bayern Munich. The season resumes later this month, with Dortmund taking on Augsburg on Jan. 22.