Vijender and Losan will square off on March 19 in a super middle-weight (76kg) showdown in Goa
Though dejected, Vijender put up a brace face, saying he would come back stronger.
The referee, after one minute and nine seconds in the fifth round, declared the Russian winner as the eight-round game ended in a knockout.
'It's good to be back. We start our season with a victory. It wasn't easy to fight against (Sulley). Will return to the gym in a week and will fight again in December or January'
Unbeaten so far, Vijender is unfazed and said the height of his opponent -- who stands at 6 feet 4 inches.
India's star boxer Vijender Singh does not want to carry the baggage of last year's maiden defeat on the professional circuit as he returns to the ring.