Andy Murray says Viktor Troicki and Marin Cilic were ''unprofessional'' and have no excuse for doping offenses that led to their suspensions.
Troicki had an 18-month ban reduced to 12 months this week for skipping a blood test in April, though he provided a urine sample that was negative.
Cilic served a four-month ban after testing positive for a banned stimulant in May. He claimed he didn't intend to ingest the substance, which was in a glucose tablet bought at a pharmacy.
Speaking to the BBC, Murray said there ''almost has to be zero tolerance'' for tennis to stay credible in public opinion.
The Wimbledon champion added: ''Whether either player was intentionally cheating or not - we don't know that, and I don't think either of them are like that -but both of them were unprofessional.''
Murray is sidelined from the ATP World Tour Finals in London this week while recovering from back surgery.
