The Timbers scored near the end of the first half to edge their way over the visiting Seattle Sounders.
The Timbers (13-5-14) moved into first place in the MLS Western Conference, pulling them closer to the postseason spot with two games left.
Portland will play host to the Seattle Sounders at 6 p.m. Sunday at Jeld-Wen Field in a match with enormous postseason ramifications.
Camilo Sanvezzo scored two quick goals, including one off a bicycle kick in the 78th minute that pulled the Vancouver Whitecaps into a wild 2-2 draw with the Portland Timbers in a Cascadia Cup rivalry match Sunday night.
Maximiliano Urruti scored his first Major League Soccer goal to give the Portland Timbers a 1-0 rain-drenched victory over the Los Angeles Galaxy on Sunday.
Diego Valeri scored in the 13th minute and Donovan Ricketts earned his 10th shutout of the season, leading the Portland Timbers to a 1-0 victory over the Colorado Rapids on Friday night.
Diego Valeri scored in the 50th minute to lift the Portland Timbers to a 1-1 draw against Chivas USA on Saturday night.
The Timbers added a new weapon to their offensive arsenal on Monday by picking up forward Maximiliano Urruti.
Kalif Alhassan opened the scoring in first-half stoppage time, Portland added three goals in the last 10 minutes, and backup goalkeeper Milos Kocic stepped in to earn the shutout as the Timbers beat Toronto FC 4-0 on Saturday night.
Portland had no answer for Salt Lake's precision passing early in the first half. RSL showed patience in working the ball into the attacking third and made the Timbers pay for it with a pair of early goals.
The assault happened before a Timbers game in April. Police said they tracked down two fans of the San Jose Earthquakes where they live in California and arrested them for attacking a Timbers fan who was in his car.
Eddie Johnson flicked a header past Portland goalkeeper Donovan Ricketts off a free kick in the 60th minute, and the Seattle Sounders made Clint Dempsey's home debut memorable with a 1-0 win Sunday night over the Timbers before the second-largest, stand-alone crowd in Major League Soccer history.
The Portland Timbers travel to face arch-rival Seattle on Sunday and their newly acquired superstar Clint Dempsey.
Real Salt Lake's Cole Grossman kept his focus when the Portland Timbers lost theirs.
Darlington Nagbe scored the go-ahead goal in the 33rd minute and the Timbers held on to defeat FC Dallas 2-1 Saturday night. Ryan Johnson also scored for Portland, which moved into third place in Major League Soccer's Western Conference, a point ahead of the Los Angeles Galaxy and two in front of Vancouver.