Russian Daniil Medvedev claimed his fourth ATP title of the year with an emphatic victory over Italy's Jannik Sinner in the final of the Miami Open on Sunday.Sinner had upset world number one Carlos Alcaraz in Friday's semi-final but the 21-year-old struggled in the heat against the fourth seed Medvedev, who triumphed 7-5, 6-3.The win was Medvedev's 19th career ATP title and his fifth in a Masters 1000 event and confirmed his dominance on hard courts in 2023.The Russian, who had already won titles at Rotterdam, Doha and Dubai, started confidently, holding serve to love while Sinner's first service game was a real battle.Sinner had to save a break point and fought through a 26-shot rally before coming through at the end of a 10-minute game.In contrast, Medvedev again served to love but Sinner was showing signs of settling as he held his serve and then the Italian broke Medvedev to go 3-2 up, with a deft touch volley.Medvedev immediately broke back, however, with Sinner's effort clipping the net and going out and after the Russian held again, the Italian had attention from the ATP trainer.Sinner, looking uncomfortable in the bright sunshine, took a pill along with a powder in his water in the 87 F (30.5 C) heat.Medvedev, looking composed and confident, grabbed the first set when Sinner was serving at 6-5 down and the Italian's poor shot into the net handed the Russian the crucial break.Medvedev quickly got ahead in the second set when Sinner sent a forehand long but just as quickly handed the break back to Sinner.But Sinner was making too many errors and when Medvedev broke again to go 3-1 up, the Italian was unable to turn things around and the world number five coolly completed his first ever win in Miami.