Two of the biggest surprises of the early MLS season square off at Jeld-Wen Field Friday when the Philadelphia Union takes its stingy defense to Portland to take on a Timbers side sporting a perfect record at home.

Portland is riding high after beating previously undefeated Real Salt Lake last week. The 1-0 victory showed not only that the Timbers can defend home field against a good team, but that a defense that had struggled in early games could step up and post a shutout.

The Union knows plenty about shutouts, having recorded four in six matches. Recording a fifth will need to come without two defensive starters though, with left back Jordan Harvey suspended and centerback Danny Califf expected to miss the match due to illness.

With or without Califf, Philadelphia will be hard-pressed to stop a Portland attack that has thrived at Jeld-Weld Field. Head coach John Spencer integrated Colombian playmaker Diego Charra into the starting lineup last week and started Darlington Nagbe as well. Pairing them with dangerous winger Khalif Alhassan gives the Timbers a truly dynamic midfield that will force the Union to defend with numbers.

Philadelphia may have learned a good lesson last week against San Jose, when the Union played a man down and actually went on the attack at times rather than just parking the bus. The tactic worked well and showed us a Philly side capable of being far more dynamic than the squad that managed to score just four goals in its first five matches.

A key to the Union finding success could be second-year forward Danny Mwanga, who has struggled for playing time early in the season. Philly head coach Peter Nowak has been waiting for the chance to finally pair Mwanga with Carlos Ruiz, which would allow Sebastien LeToux to move to midfield. The combination didn't produce a goal in one half together last game but could get another look.

The Union will need a strong performance from its offense to help take some pressure off what could be a patchwork back-line. Between Portland's dangerous offense, and a home crowd that has helped the Timbers defeat all three previous visitors, the Union will try to become the first team to escape Jeld-Wen Field with a victory.

Match Previews

Real Salt Lake vs. Chivas USA

RSL returns home to Rio Tinto Stadium for the first time since the disappointing Champions League Final loss to Monterrey. Standing in the way of a positive rebound is a streaking Chivas USA side that has given up just one goal in four matches.

Chivas USA showed off an offense that could actually generate chances last week, but they won't find opportunities as easily against an RSL defense that has to be eager to post a shutout and remind us why it was the stingiest defense in the league in 2010.

Offensively, RSL should welcome back Javier Morales and Kyle Beckerman as a tandem, arguably the best central midfield combo in MLS. One thing is clear: The Rojiblancos haven't faced a playmaker like Morales during its recent stretch of shutouts. Look for RSL to flex its muscles and bring Chivas USA back to earth.

Toronto FC vs. Houston Dynamo

TFC is a frustrating team to figure. Two of its past three matches have been putrid efforts in 3-0 losses, but the Canadian club has also mixed in an impressive draw against Columbus and an early tie versus Los Angeles.

Toronto will need a top effort against a Houston side still reeling from a shocking mid-week loss to Colorado. An awful Tally Hall blunder followed by a scrappy winner for the Rapids snapped Houston's six-match unbeaten streak.

How will the Dynamo respond? Depends on which TFC side shows up. If it's the good Toronto, then Houston could be lucky to settle for a draw. If it's the awful Toronto? The Dynamo is capable of scoring a big win that will force frustrated Toronto fans to lose even more patience.

New England Revolution vs. Colorado Rapids

The Rapids have to be riding high off an improbable mid-week win against Houston, but now comes a road trip to the Boston area to take on a Revs side licking its wounds after being embarrassed by Chivas USA.

The battle in central midfield will make for must-watch action. Benny Feilhaber and Shalrie Joseph versus Pablo Mastroeni and Jeff Larentowicz will likely turn into a stalemate, meaning the game will be won and lost elsewhere.

Where exactly? On Colorado's right flank, where Omar Cummings will look to take advantage of the likely absence of Revs left back Didier Domi. If the Revs can find a way to contain Cummings, the Revs should rebound from that awful showing last week.

Columbus Crew vs. Seattle Sounders

Chad Marshall's uncertain status could definitely jeopardize the Crew's unbeaten streak, facing a Sounders side that played a mid-week game in D.C. If Marshall can't go, Columbus will turn to disgruntled reserve Andy Iro, who could have his hands full with Fredy Montero. The bigger question will be whether the Crew can handle the Sounders flank players, with the Brad Davis-Sebastian Miranda match-up one to watch closely.

For Seattle, Sigi Schmid will have to seriously think about his defense and who should be starting at centerback. Jeff Parke has been benched lately after a solid start to the season, but his physicality will be needed against the Columbus forwards.

If Marshall is healthy, the Crew should be able to hold the Sounders off. If Marshall can't play, look for Seattle to take advantage and escape Crew Stadium with a point or three.

D.C. United vs. FC Dallas

Charlie Davies and Josh Wolff were thoroughly impressive as a tandem in the mid-week win against Seattle, but it was the inclusion of Andy Najar after a stretch on the bench that was the real news for D.C. Najar's dynamic ability gives the United attack another element and will be key to turning around a rough stretch of results.

For Dallas, two straight wins since the injury to David Ferreira shows the squad still has plenty of talent, but the defense will face one of its tougher tests to date. It will be up to the Dallas attack to go after United's defense, which was bailed out by a standout performance from goalkeeper Bill Hamid at midweek.

Dallas has the players to score a road win, but D.C. United gained some serious confidence from its mid-week win and should get on a roll behind Davies and Najar.

Chicago Fire vs. Vancouver Whitecaps

Two teams in dire need of a win face off in a tough match-up to measure. Neither team has won since March, though the Fire come in with some confidence off a 1-1 road draw against Colorado.

Chicago tried a new midfield combo, with second-year playmaker Corben Bone showing some glimpses playing alongside Daniel Paladini and Gaston Puerari. The Whitecaps aren't nearly as tough in the middle as Colorado is, so the Fire will look to control possession.

The key for Vancouver will be getting the ball to midfielder Davide Chiumiento, who will look to go at Gonzalo Segares. Even though Chicago hasn't traditionally done well at home, look for the Fire to snap its winless streak with a strong defensive effort.

Los Angeles Galaxy vs. New York Red Bulls

The battle of star-studded squads is the game of the week. There are storylines galore, from the five designated players likely to take the field, to the first Beckham-Henry battle in MLS, to Juan Pablo Angel's first meeting against his former team.

On the field, a big question for New York is whether Teemu Tainio will be available. Without him, the Red Bulls could struggle to win the midfield battle. With a fit Tainio, the Red Bulls have the midfield to counter what should be an aggressive approach from Los Angeles.

The Thierry Henry-Omar Gonzalez match-up will be a fun one to watch, but A.J. De La Garza will need to be on his toes against either Luke Rodgers or Juan Agudelo, two forwards very capable of beating him.

The Galaxy will need to find a way to beat a stingy Red Bulls defense that has allowed just two goals this season. Landon Donovan is the key to the Galaxy attack. His speed can disrupt New York on the flank, something we saw Kansas City's Ryan Smith do to Jan Gunnar Solli.

Look for Juan Pablo Angel to play his best game since joining Los Angeles, with the Galaxy edging the Red Bulls in a hard-fought encounter.

Ives Galarcep is a senior writer for covering Major League Soccer and the U.S. national team.