Belgium unveils preliminary World Cup squad; Nainggolan left off

Radja Nainggolan isn't even in consideration to make Belgium's final World Cup squad.

The Roma midfielder was contentiously left off his international side's 28-man preliminary list on Monday by manager Roberto Martinez.

Martinez did, however, shed light on Nainggolan's omission, referring to it as a tactical decision.

"(Nainggolan) is a top player. The reason is tactical. In the last two years, the team has worked in a specific manner. Other players had those roles," he said.

"We know that (Nainggolan) has a very important role in his club and we cannot give him that role in our squad."

Nainggolan, who has earned 30 caps for Belgium but also wasn't named to its 2014 World Cup squad, apparently wasn't satisfied with Martinez's selection criteria, however. After being snubbed for this summer's tournament, the 30-year-old took to social media to announce he's retiring from international play.