CHICAGO -- The Bulls announced Wednesday night that forward Lauri Markkanen's season is over for precautionary measures while he undergoes additional medical testing over the next 10 to 14 days to determine why he suffered a rapid heart rate and fatigue during Tuesday's loss at Toronto.
The Bulls said initial tests to determine the cause of the problem have come back normal.
"The long-term health of our players is always our organization's top priority," Bulls executive vice president of basketball operations John Paxson said in a statement. "We will continue to monitor Lauri's condition and work with our medical staff and doctors to provide him with everything he may need."
The 7-foot forward from Finland was averaging 18.7 points and 9.0 rebounds in his second season.
"Obviously, we're disappointed for Lauri, and for us. But we're hopeful that he'll be just fine," coach Jim Boylen said.
Markkanen was evaluated in the training room by the Bulls' medical staff and Toronto's team physician after exiting in the first half of Tuesday's 112-103 loss. He underwent more tests at a hospital following the game and remained in Toronto overnight.
Earlier Wednesday, Boylen said Markkanen was in his office asking to play against Portland following an examination by doctors in Chicago.
Markkanen's setback is the latest in a long line for the Bulls this season.
Leading scorer Zach LaVine (bruised right thigh, right knee tendinitis), Otto Porter Jr. (strained right rotator cuff) and Kris Dunn (back) also sat out Wednesday's 118-98 loss to Portland. In addition, Wendell Carter Jr., Chandler Hutchison and Denzel Valentine are recovering from season-ending injuries.
Information from The Associated Press was used in this report.