Carlos Alcaraz got his maiden ATP Finals campaign back on track with a win over Andrey Rublev in which the Russian hit himself so hard with his racquet he drew blood.
Wimbledon champion Alcaraz had lost to Alexander Zverev in his Red Group opener on Monday but the Spaniard returned to beat Rublev 7-5 6-2.
It was a second defeat for Rublev, who lost to Daniil Medvedev on Monday, and means he cannot reach the semi-finals.
Zverev faces Medvedev later in the day.
World number two Alcaraz got the key breakthrough in a tight opening set in the 11th game and then served out the set.