http://brainking.com/en/ShowGame?g=1412606

Will someone take a look at this game and tell me about Sergeys last move here?

He is ranked quite high so I assume he knows what he is doing, but to me, since he doesnt have to gammon me why would he take such a chance on this move? It seems to have worked out for him, but I was surprised he didnt just cover up and go from there? to leave me with a chance to hit him back and even get a 6 1 seems really risky to me. But maybe thats why I dont do so well at this game? Thanks for your input!