Lokomotiv Moscow could face UEFA sanctions following their 2-0 loss to Turkey's Fenerbahce in the first leg of their Europa League round of 32-tie.
Tensions have been high between Russia and Turkey since the latter shot down a Russian jet after it violated its airspace near the Syrian border in November.
Lokomotiv's Russian midfielder Dmitri Tarasov pulled off his shirt to reveal a portrait of Russia president Vladmir Putin after his side's defeat which puts his team on the cusp of a Europa League exit.
Beneath the portrait, the shirt read in Russian: "The most polite president."
UEFA do not allow political statements in their competitions.
After the match, Tarasov told Russian agency R-Sport that he was simply proud of Putin.
''It's my president. I respect him and decided to show that I'm always with him and prepared to give my support," he said.
''What was written on that shirt was everything that I wanted to say.''
Turkish media reported that the Lokomotiv bus was pelted with bottles as it approached the Sukru Saracoglu stadium.
Reports say Turkish police detained three people in Istanbul before the match as a result of the incident.