After some paperwork delays, Argentine international midfielder Mauro Rosales has been officially signed by the club. He trained with the team for the last few weeks of the preseason and seems to bring a lot of talent for a non-DP contract. He's a fast, skilled midfielder who can play either on the wing or in the middle. It's not clear whether he'd be ready to play in tomorrow's match versus the Red Bulls. If Zakuani's out, he could potentially be useful on the wing, but it seems he generally plays on the right rather than the left (though Zakuani is inverted himself).
His addition complicates the midfield situation. With Alonso locked into the holding midfielder slot and Zakuani (when healthy) into the left wing, there are two midfield starting positions to divide between Alvaro Fernandez, Brad Evans, Erik Friberg, and Rosales, all of whom seem to have the ability to be solid MLS starters.
Update: Enjoy some YouTube.