Mourinho was snapped handing a stylish black box to Berdyev before the second-leg of the Europa League tie, which Manchester United won 1-0.
There was a wealth of speculation online as to what the box contained, with Rostov posting a picture of the gift to their Twitter page.
The image showed a small replica of the Europa League trophy with the Manchester United crest emblazoned on it and ‘FC Rostov, Round of 16, 2016/17’ written underneath.
Rostov posted the image along with a message reading: ‘Inside the black box from Jose Mourinho was this super-cool keepsake!’
В черном ящике от Жозе Моуринью был этот шикарный памятный сувенир
— Football Club Rostov (@rostovfc) March 20, 2017
Relations between the two clubs during their Europa League tie were extremely cordial, with Rostov handing out free blankets to the 200-strong group of United fans that travelled to Russia for the first-leg.
The red blankets, which had “Gentlefan Russian Warm Welcome” written on them in white lettering, did not go unnoticed by Mourinho, who praised Rostov’s hospitality.
“I think everything was magnificent. People were nice to us since we landed,” he said after the first-leg, which ended 1-1.
“My view is that everything went wonderfully well in Russia – apart from the pitch, but the club was so nice to us, the people around the hotel and the airport were so nice to us.”