Topalov, who will turn 41-years-old during the Candidates tournament, is the least active among the players in the competition. He would definitely be an interesting challenger for the title. On one hand, he seems to be past his prime, and fans almost certainly want a young challenger against Magnus Carlsen. But Topalov beat Carlsen not once, but twice, in 2015!
Read more about Veselin Topalov here.