Speaking to the German FA's website, Werner said: “Personally, it wasn't the very best time.
“I had imagined something more. I learned a lot, won the Champions League and other trophies.
“I enjoyed the two years abroad very much – and enjoyed London very much. I had one laughing eye and one crying eye.
“In Leipzig, not everything went so smoothly in the first few weeks, but the football under the new coach suits me very well and prepares me for what is required in the national team."