[MLS SPOTLIGHT] Fans of the Philadelphia Union are understandably nervous as their team prepares for the final phase of preseason training in Costa Rica. The Union will scrimmage Municipal Perez Zeledon on Sunday and next week does the same against Costa Rica's U-20s and Belen before returning to Philadelphia. Coach Peter Nowak says the trip offers his players a change of pace; it also suits the secretive sessions he's often conducted during preseason since the team launched in 2010.

Two crucial pieces of year’s playoff team departed in surprising circumstances: goalkeeper Faryd Mondragon opted for a return to his Colombian roots rather than follow up his impressive 2011 debut in MLS, and top scorer Sebastien Le Toux went to Vancouver in a trade while complaining bitterly the team tried to force-feed a transfer to English club Bolton.

Philly believes it has a ready-made replacement for Mondragon; a contingent of attackers will try by committee to compensate for the loss of Le Toux, who scored 25 goals and contributed 20 assists in two excellent seasons.

Last year’s backup in goal, Zac MacMath, is penciled in to replace Mondragon. The 20-year-old has just eight games of MLS experience, which he gained late last season after a broken finger sidelined Mondragon. Veteran defender Danny Califf has taken over the captain’s armband worn by the Colombian keeper last season, and he believes the American understudy is ready to step up.

“I think Zac’s got a huge upside,” says Califf, who like MacMath played at the University of Maryland and came to the pro ranks through U.S. Soccer’s youth teams. “I think he really helped us last year, and I can’t see any reason why he won’t be as good as he was last year.

“So it’s going to be exciting. Faryd did a great job and was an incredible leader, but Zac’s a young kid and he moves better. He’s the future. Mondi’s got those intangibles you just can’t teach, but Zac’s got the youthful enthusiasm.”

MacMath is trying not to alter his preseason preparation now that he’s projected to be the starter, and regards any action against players other than his teammates as invaluable. “Hopefully I’ll get a couple of good games in to get sharper and build up more and more confidence,” he said prior to the team’s Thursday departure. “You can only practice so much and it’s only in game situations that you’re judged truly where you are.”

During a busy offseason the Union acquired more than a dozen new players. The continent includes forwards Josue Martinez (Costa Rica) and Lionard Pajoy (Colombia), and midfielder Gabriel Gomez (Panama). Along with draft pick Chandler Hoffman, and returnees Freddy Adu, Jack McInerney, Danny Mwanga, and Roger Torres, there’s many attacking options from which Nowak may choose.

At this point in the preseason, the attack is impossible to evaluate. The Union scored seven goals in three games during a trip to Florida, but the opponents were Florida Gulf Coast University, the University of Central Florida, and Orlando City of USL Pro.

A new contract for right back Sheanon Williams, who has graduated from the Harrisburg City Islanders to take his place among the league’s best right backs, was announced shortly before the team flew to Costa Rica. He’s one of the league’s success stories, a starter in all 40 of his appearances since leaving the Islanders to join the Union in September, 2010.

Last year, along with the additions of defender Carlos Valdes and Mondragon, his steady play helped the Union post 10 shutouts and limit opponents to 36 goals in 34 games, tied for second-best in MLS.

“The past 18 months has been an amazing experience and I'm very excited to remain in Philadelphia,” said Williams when the deal was announced. “I would like to thank the organization for their confidence in me and the fans for their incredible support. We made a lot of progress last season but have a lot more work to do to achieve our goals in 2012 and beyond.”

The newcomers as well as the incumbents are being drilled from Nowak’s famous playbook, which details the formations and strategies, as well as the philosophies, by which he manages his team.

“We’ve got to be prepared for different scenarios,” he said in a conference call with reporters Wednesday. “They’ve got the playbook, but how to work with imagination. The last thing you want, really, is to give them a playbook and basically run the schemes. At some point the players make their own decisions and decide what’s best in different situations.”

Philly returns from Costa Rica a week from Sunday and then has another week to prepare for its opener, a Monday night match March 12 at Portland to be shown live on ESPN2/ESPN Deportes.