Is that really gambling?  In a tournament, don't you pay an entry fee and then hope to get lucky?  So you're competing against dozens of other entrants, not against just one, or against the house.  Or did he even have to pay to enter the tournament?  Maybe players were invited for a publicity event. 

Google AI says, "Form 1099-MISC Miscellaneous Information is used for prizes and awards from sweepstakes or other games that do not involve a wager. The winnings are reported in Box 3. A 1099-MISC is issued for prize winnings of $600 or more."  

I would ask the taxpayer if he paid to enter the tournament.  And I would suggest he ask the casino why they reported it on a 1099-MISC.