It was in mid-December that Mirza Teletovic of the Nets first began feeling, in his words, “weak, weird and kind of dizzy.” Initially, though, there was no discernible reason.

He found himself losing his breath after just one or two trips down the court. His family noticed that he was exhausted and was going straight to sleep after games and practices. Surprised that he might be out of shape, Teletovic began doing extra conditioning work on the treadmill. But nothing seemed to help.

The mystery was solved on Jan. 22. During a game that night at the Los Angeles Clippers, Teletovic experienced shortness of breath that was worrying enough that he stopped playing and was taken to a hospital. Tests revealed blood clots in the arteries of his lungs, a potentially fatal condition. He was placed on a blood-thinning medication program, and his season came to a sudden end.

“You feel terrible, scared,” Teletovic said Monday before the Nets earned a 110-108 home win over the Golden State Warriors. “What’s going on? Why do you have it? Why’s it happening?”