TURIN, Italy—Novak Djokovic advanced to the semifinals of the ATP Finals by beating Andrey Rublev 6–3, 6–2 on Wednesday. The top-ranked Djokovic is attempting to match Roger Federer’s record of six titles at the season-ending event for the top eight players in the world. Djokovic was again almost perfect on his serve, although Rublev managed to break him in the opening game. Djokovic broke twice in each set and won the match with his 12th ace. “I knew that I had to be on my toes and start well,” Djokovic said. “I dropped my serve again like in the first match. It was quite a nervous start from both of us until 4–3, then with new balls I somehow managed to find the right shots at the right time. “Winning the first set I put additional pressure on him, and I started to maybe play more consistently from the back …