Toronto FC defender Drew Moor will miss at least this weekend's game after the discovery of an irregular heartbeat.
The MLS club announced Moor's condition on Friday and said more tests would be conducted next week.
A team statement said: "During a medical examination following a training session this week, a cardiac arrhythmia was discovered in defender Drew Moor. Further testing is necessary to determine diagnosis and management, which will take place next week.
"As precaution, Moor will not travel to Columbus for this weekend's match against Columbus Crew SC."
Moor, 33, is in his second year with Toronto FC and his 13th season in MLS. He had played every minute of Toronto's five games so far this season. He is a U.S. international with five caps, though the most recent came in 2008.
A similar ailment sidelined Seattle Sounders forward Clint Dempsey for the second half of last year before he was able to return at the start of the 2017 season.
