World Cup reporter Grant Wahl's fatal collapse during a match Friday is a tragic end to a long, arduous week of illness -- something he openly discussed the day before his death.

Grant recorded and posted his "Fútbol with Grant Wahl" podcast on Thursday, and said he'd come down with a case of bronchitis so bad ... he'd "been to the medical clinic at the media center twice now, including today."

Grant added he was feeling better, but was far from 100% ... which he said listeners could probably hear in his voice.

As we reported, the veteran sports journalist collapsed Friday -- while covering the Argentina-Netherlands match -- and after CPR attempts at Lusail Stadium, he was Ubered to a hospital, but died. CBS News is reporting it was a heart attack.

Grant's brother, Eric, announced his death with a video -- in which he was understandably distraught -- and flat out said he believed there was foul play involved.

He said Grant had been getting death threats in Qatar after stadium security had detained him back in November ... when he wore a rainbow-themed T-shirt in support of LGBTQ+ rights. His detainment became a big story, as Qatar had threatened to shut down any LGBTQ+ protests during the tournament.

Grant's death shocked the sports world, well beyond the World Cup -- he'd covered huge athletes for Sports Illustrated during his career, including then-high school phenom LeBron James' famous SI cover story.

Friday night, LeBron remembered Grant fondly, saying ... "It's unfortunate to lose someone as great as he was. I wish his family the best and may he rest in paradise."

Grant was just 49.