Mexico City, then, became the obvious choice, particularly because the stadium was already receiving upgrades as part of a 50th anniversary celebration. The NFL poured on the improvements, too -- among other things, it constructed new locker rooms because the existing ones weren't large enough to accommodate 53 players. The other appealing part of Mexico for the league: Unlike games in London, which, because of the time difference, can only be played in the early afternoon for broadcast on Sunday mornings in the United States, games in Mexico City, which is in the Central time zone, can be played in the highest-profile Sunday and Monday prime-time slots. For teams, concerns about travel length and time changes are diminished, but they'll be forced to focus instead on dealing with Mexico City's altitude (over 7,200 feet above sea level, about 2,000 feet higher than Denver), a factor that will prompt some teams to arrive later in the week and depart immediately after the game. Waller says teams really have two options: either arrive early to adjust to the altitude or swoop in very late to minimize the overall impact on players. The Raiders and Texans, according to Waller, have chosen the latter: spend as little time as possible at altitude, get in and get out quickly.