After his two goal performance in Real Madrid's 3-0 victory over Granada Sunday, forward Cristiano Ronaldo said he did not celebrate his goals because he was "sad".

The superstar 27-year-old later attributed his dour mood to an issue with Los Blancos management, and ever since speculation has grown as to what could be bothering him.

Here are four reasons that reportedly could be upsetting the Portuguese native.

A New Contract

While Ronaldo has insisted his issue with Real has nothing to do with money, consider that he is actually the 10 th highest paid player in his sport, earning 10 million a season. Too often players associate the tag of "highest paid" as a sign of respect from their clubs. This could be one reason for Ronaldo's shift in mood.

Rumors swirled with Ronaldo transferring to Manchester City, but they were seen by many as ways to gain leverage on Real to negotiate a new deal. Ronaldo has denied his sadness has anything to do with money.

Teammates

The star could also have some trouble with one of his teammates. Ronaldo and teammate Marcelo have little to no relationship, according to BBC Sports.

On the flip side, BBC reported Ronaldo may also have a problem with how Real has treated his friend and teammate Fabio Coentrao, who takes a lot of criticism from the Madrid press.

Light Transfer Market

Los Blancos brought in midfielders Luka Modric and Michael Essien during this summer's transfer market but Ronaldo was reportedly unsatisfied. According to Yahoo Sports!, Ronaldo had a very "specific" player in mind, who could complement his play, but Real were unable to pull the trigger for the mystery player.

UEFA Euro Player of the Year

Last week, Barcelona's Andres Iniesta won the coveted award, edging out teammate Lionel Messi and Ronaldo, who was noticeably annoyed during the ceremony. While this loss can't be attributed to Real Madrid, it could still affect a known sensitive player like Ronaldo.