So "gagging" in this sense is synonymous with "choking", then ... in which case it strikes me as an odd usage, in that, to my mind, when a professional athlete "chokes", it is an anomaly; otherwise, the athlete in question wouldn't be professional - so, for example, a basketball-player might "choke" when he's taking the foul shot that will win or lose the game, and miss the basket. The idea of a whole field of professional athletes "choking away" is almost comedic - but maybe that's what happened ... ?