Top challengers to Team USA

Spain, led by Jose Calderon and Pau and Marc Gasol, will be Team USA's fiercest competition. Janek Skarzynski/Getty Images

Although Spain is the biggest threat to unseat Team USA as Olympic basketball champion, a number of teams in the tournament could pose problems for Mike Krzyzewski's squad. Brazil and Argentina already have shown that they can give the Americans headaches.

It's important to keep in mind that after pool play, the top eight teams are seeded into quarterfinals -- with one loss keeping a team from winning the gold medal. Is it likely that Russia or Lithuania could pose big problems for the red, white and blue? No, but in a shorter, 40-minute FIBA game, the potential for an upset is real. Factors like foul trouble (with five fouls disqualifying a player) and the occasional cold shooting night from a key player can be critical.

Here is my ranking of the teams that pose the biggest threat to upset Team USA in London.

1. Spain

Seven players on Spain's roster have played in the NBA, and their success in the league makes it the top threat to unseat Team USA as the reigning Olympic champion.

The brothers Gasol, Pau and Marc, are NBA All-Stars. Serge Ibaka, who's 23 years old, played in the NBA finals and finished second in the voting for NBA defensive player of the year. Point guard Jose Calderon finished fourth in the NBA in assists this past season. Euroleague star Juan Carlos Navarro was a second-team all-rookie in his only NBA season.

In addition to its talent, Spain has great continuity. The core of the team has been together for a while and is in the midst of a great run that includes a FIBA World Championship in 2006, an Olympic silver medal in 2008 and the past two European Championships.