(Photo credit: John Hefti) The San Jose Earthquakes will try to extend a five-match unbeaten run on Saturday night when they host a Portland Timbers team missing both of its starting center backs. After losing four in a row to begin August and continue a midseason tailspin, the Quakes (12-8-6, 42 points) have rebounded to reclaim their status as Western Conference contenders. Manager Bruce Arena's gro