Manchester United was No. 1 at $1.86 billion, followed by the Dallas Cowboys ($1.81 billion), New York Yankees ($1.7 billion), and Washington Redskins ($1.55 billion).
According to Forbes, Real Madrid's gross annual revenues of $537 million were second only to the Yankees in all of sports.
So Real Madrid is in some pretty heady company.
"We have 300 million fans worldwide," team official Emilio Butragueno said in a recent phone interview. "Our marketing department has done a great job, and we have been able to adapt ourselves to the growth of the communication industry."
Real Madrid can demand top dollar. A source said the team would be paid $2.3 million for its appearance on Saturday, the team's third and final stop on a U.S. tour.
Despite the team's popularity, Butragueno said Real Madrid sees room for growth in the United States.
"One of the reasons we have been traveling here is we would like to solidify our fan base in the U.S.," he said.
The team's first two games on its tour of the States drew big crowds, but they were far from sellouts.
Real Madrid beat the Los Angeles Galaxy, 4-1, on Saturday before 56,211 at the Los Angeles Coliseum, and then scored a 3-0 win over Chivas Guadalajara on Wednesday at Qualcomm Stadium in San Diego before 38,211.
"The U.S is very important for us and we like coming here so our fans can have direct contact with our players, go to the games, and little by little our relationship with them is getting better," Butragueno said. "We think the U.S. and Asia are two growing areas in the future."
The team's biggest attraction is 26-year-old Portuguese superstar Cristiano Ronaldo, who scored a hat trick in Wednesday's win. In an e-mail response to The Inquirer, Ronaldo said he was eager to make his first appearance in Philadelphia.
"I have actually never played in Philadelphia because I was transferred to Manchester United from Sporting [Lisbon] immediately after they played Barcelona in 2003 to open up Lincoln Financial Field," he said. "I have heard that Philadelphia has very passionate sports fans, so I'm looking forward to playing there for the first time."
Last year's friendly at the Linc against Manchester United drew 44,213 fans. A source said Thursday that sales for this game were close to 50,000.
Regardless of what the final figures will be, the Union are involved in another big soccer event, anticipated by Philadelphia fans and yes, the players as well.
The Union got a taste of top international competition with Wednesday's 1-0 win over Everton of the English Premier League before a sellout crowd of 18,582 at PPL Park in Chester.
"Real Madrid is one of the best in the world, and the game against Everton gives us an idea of what we will be facing on Saturday," Union forward Danny Mwanga said. "Hopefully we will work harder, and we know it's going to be a tough challenge."
Contact staff writer Marc Narducci at 856-779-3225, email@example.com,
or @sjnard on Twitter.