Kristaps Porzingis is struggling in the playoffs due to a mysterious illness he can’t explain, calling it heartbreaking and physically draining.

The Boston Celtics have struggled to get a strong showing from Kristaps Porzingis, who is still dealing with a linger illness from the winter.

When Kristaps Porzingis concluded his first six-minute shift Wednesday night, he looked like he’d just run a marathon. His breathing was heavy. He was visibly fatigued. When he took his seat on the Celtics bench, he dropped his head and stared at the TD Garden parquet.