The Russia international has netted two goals in as many games since his arrival from Stuttgart last month.
But despite his promising start, the 28-year-old has noticed a different after adapting to English football from Germany's Bundesliga.
“I haven’t been this exhausted for a long time. The match was very intense, hardly any pauses," he told Sport-Express.
“Tough challenges and big powerful defenders are difficult to adjust to initially.
“Aside from that, I was very pleased with the support – I have never seen so many away fans at a stadium.
“I am in a great mood, of course. I never expected to get off to such a good start. Hopefully my form will continue.”