MLSÆs 2006 semifinalists will be determined this weekend with the second leg of the quarterfinal series, which are decided on aggregate goals. HereÆs Soccer America Senior Editor Ridge MahoneyÆs take on the four clashes this Saturday and Sunday.

New England-Chicago
(Chicago leads, 1-0)
Saturday, 7:30 pm ET. TV: Fox Soccer Channel, Direct Kick.

The Revs are only one goal down but are also two players short, give or take a sprained ankle. Shalrie Joseph is suspended and Clint Dempsey is hobbling from the effects of a crunching C.J. Brown tackle in the first match in Chicago.

Andy Dorman is being justifiably ripped for turning away from Justin MappÆs free kick as it zipped into the net, yet had Taylor Twellman put away a header from a Dorman chip the teams would probably be tied, 1-1. DormanÆs incisiveness can decide this match; he glided into good positions last weekend only to hit poor crosses or shoot weakly.

Pat Noonan underwent sports hernia surgery in Germany just two weeks ago but has been training and can play if the situation is dire. His poised touches will pierce the FireÆs defense if he can find seams in ChicagoÆs three-man back line or spaces behind midfielder Chris Armas.

Without Joseph patrolling midfield, the task of tracking ChicagoÆs busy attackers is difficult. Andy Herron, Ivan Guerrero, Chris Rolfe and Mapp will cause problems, as will 6-foot-3 Nate Jaqua. The Revs canÆt surrender a lot of possession; they need to keep the ball and carve out good chances; Fire keeper Matt Pickens played well last week but most of his saves were fairly routine.

Dallas vs. Colorado
(Dallas leads, 2-1)
Saturday, 8:30 pm ET. TV: Direct Kick.

None of the omens look good for the Rapids, who deserved at least a tie last week but were victimized by a few tough officiating decisions and their own ineptitude.

Thiago Martins terrorized the Dallas defense last week, but heÆs been suspended for throwing an elbow. Pablo Mastroeni replaced the suspended Mike Petke in the back line, and midfielder Kyle Beckerman responded with a solid two-way game. Somebody, though, needs to score goals or set up Nicolas Hernandez. Mastroeni may be needed in the back line again, as Aitor Karanka left the game last weekend with a strained hamstring and is listed as questionable for game two.

Without Martins, Coach Fernando Clavijo has few options up front, with Clint Mathis sadly ineffective, Jovan Kirovksi out of form, and Fabrice Noel extremely inexperienced.

FC Dallas certainly has defensive problems, as the Rapids demonstrated. But it has more firepower, efficient goalscorers in Kenny Cooper and Carlos Ruiz, and on its home surface at Pizza Hut Park should be able to control the midfield.

D.C. United-New York Red Bulls
(D.C. leads, 1-0).
Sunday, 6 pm ET. TV: ESPN2.

First goal wins, if itÆs the home team, because if United gets the lead and goes into management mode, itÆs over. Nobody is more effective and ugly holding a lead, especially in the playoffs. Alecko EskandarianÆs finishing looked a bit rusty in the first leg; heÆll be sharper in game two and should get chances to redeem himself.

The former MetrosÆ magic triangle of Youri Djorkaeff, Markus Schopp and Amado Guevara is capable of a breakthrough, but not playing from two goals down. They have the talent to get the goals yet front-to-back donÆt have the personnel to hold off a D.C. United playing for keeps unless the likes of Marvell Wynne and Seth Stammler play the best game of their young professional lives.

If the Red Bulls tie the series, 1-1, United should buckle down and squash the annoying pest, except that last year it was bounced out of the playoffs by Chicago, 4-0, at RFK. A team that misfired during the last month of the regular season could also seize up enough to keep the outcome in doubt. That isnÆt likely with Jaime Moreno and Christian Gomez on the field.

Houston-Chivas USA
(Chivas USA leads, 2-1)
Sunday, 8 pm ET. TV: Fox Soccer Channel, Direct Kick, HDNet.

The Dynamo should have come out of Home Depot Center with a tie, irrespective of one penalty kick not called and a dubious one that was called being saved.

Coach Dominic Kinnear has a tough call up front. Paul Dalglish is not a bad player but has yet to forge a consistent understanding with Brian Ching. Alejandro Moreno may not be as talented, yet heÆs quick, dangerous and aggressive, and has played several seasons not only with Ching but also with playmaker Dwyane DeRosario, who is due for a monster performance.

Brian MullanÆs game last week conjured images of him scything past defenders and drilling balls into the box as he did a few years ago. If he repeats that effort, and left-sided Brad Davis stops hitting pretty balls and launches effective ones, Chivas USAÆs defense will be punctured no matter what keeper Brad Guzan does.

The wild card is Jonathan Bornstein, a bit rattled perhaps in his first playoff game aside from a few good moments. He also had to chase Mullan for much of the game, a dynamic û no pun intended û that favors Houston.