[MLS] The start of the season doesn't end the process of altering and adjusting MLS rosters.

Players can be registered until April 15, and though the chances are slim that any major signings will occur before Wednesday, several recent acquisitions have been waiting in the wings until their paperwork is completed.

In New York, master tinkerer Juan Carlos Osorio will probably unveil one new player this weekend when the Red Bulls host Houston and might give another his first start, with another signing still awaiting the receipt of his international transfer certificate at MLS offices.

While the Dynamo are adjusting to life without Dwayne De Rosario (Toronto), Nate Jaqua (Seattle) and Eddie Robinson (injured), Osorio is just giving his team its semiannual makeover.

Last year, he added four international players in the middle of the season, and has retained only two them, midfielders Juan Pietravallo and Jorge Rojas, and more changes are afoot for the 2008 MLS Cup finalist.

Spanish midfielder Albert Celades has finally been cleared to play a competitive match with the receipt at MLS offices of his international transfer certificate. He's been with the team for nearly two months, including a 2-1 win over Velez Sarsfield in late February during the team's trip to Argentina, and has been recovering from a thigh injury while the paperwork has been finalized.

Even if Celades isn't sufficiently fit to go 90 minutes on the Meadowlands artificial turf, he's looking spry enough in training to get the start if no other problems arise. That complicates the selection process for Osorio, as rugged holding midfielder Seth Stammler is also regaining fitness after suffering a torn meniscus during the 2008 playoffs, and the coach also has Luke Sassano and Sinisa Ubiparipovic as options in the middle in addition to playmaker Rojas and holding type Pietravallo.

Right back Carlos Johnson debuted last weekend against Chicago, coming on a substitute in the 62nd minute. He'd been on international duty for Costa Rica during the recent FIFA fixture dates, but didn't get on the field against Mexico and El Salvador. He replaced rookie Jeremy Hall and is an obvious candidate to get the start versus Houston in a matchup of 2008 playoff teams that have yet to win a game this season.

Had Johnson played against El Salvador, he'd have faced defender Alfredo Pacheco, whose acquisition on loan from FAS was completed last month but travel complications prevented him from arriving in the U.S. until this week. He played the full 90 minutes in El Salvador's 2-2 tie with the USA and 1-0 loss to Costa Rica, and Osorio is eager to get his attacking skills added to a left flank that has lost the subtle talents of Dutchman Dave van den Bergh, who was traded to FC Dallas in the offseason.

The Red Bulls have scored only one goal in three games -- and that was put into the Revs net by New England defender Jay Heaps.

If Pacheco's's ITC is received in time, he would be eligible to play against Houston, which might face a radically different team than one that thumped the Dynamo, 3-0, last November and ousted the defending champion in the Western Conference semifinals.