Tennis star Andrey Rublev is going to need some bandages for his knee for the next few days ... 'cause he bloodied himself during a wild temper tantrum in a match on Wednesday.
Rublev's explosion happened while he was going up against Carlos Alcaraz in the ATP Finals in Italy.
Rublev had been trying to go toe-to-toe with the tennis superstar ... but when Alcaraz got the better of him one too many times, Rublev snapped.
Check out video from the court ... the 26-year-old smashed his racket into his knee six straight times -- opening up a gash that required medical attention.