Thursday night NFL football puts additional burden on the NFL players. By having three nights of NFL games a week, the league has increased the number of games played per season and has thus increased the number of injuries and at the same time decreased the amount of time between games for recovery. If a team has a monday night game and Thursday night game the following week, players do not have a full 7 days to recover from previous injuries caused by play.
When playing on Thursday nights, the teams involved suffer from a decrease in practice time, while the players themselves have less time to recuperate from the previous Sunday's game (on a normal schedule). This would not be the case, however, following a bye week. Plus, playing on a Thursday night could provide an advantage for the following week's game, so in the long run it may balance out.
NFL Thursday night games will give athletes a chance to enhance the quality of play rather than have it be negatively affected. And as far as I am concerned, the more games the better. This is good for the NFL and good for the sports fans and networks as well.
I believe that NFL Thursday night games may have become a self-fulfilling prophecy, but they are not negative in and of themselves. The quality of play on a Thursday night as compared to a Sunday night should be neither worse nor better. This year alone, the NFL is working with networks to expand the Thursday night slot for games, even including some double-headers. I don't believe that what night or day of the week a game is played on should have any effect on the game being played.