Real Salt Lake (16-10-8) clinched a top-two seeded position heading into the MLS playoffs. RSL can clinch the top seeding in the West if Chivas beats or draws Portland on Saturday.
Chivas (6-19-8) threatened a late rally after a goal from reserve forward Julio Morales in the 77th minute, but the Goats couldn't bridge the gap and fell to RSL for the third time this season.
RSL got on the board in the 49th minute when Saborio slotted a penalty kick inside the right post.
Salt Lake took a two-goal lead in the 52nd minute on Plata's goal. After a failed attack by Javier Morales, Plata collected the ball outside the 18-yard box and fired it down the middle, burying a low shot inside the left post.
Morales scored when he got behind Tony Beltran and latched onto a long cross from Carlo Chueca. Morales drew goalie Nick Rimando off his line and slipped the ball past his left side for the goal.
Salt Lake controlled possession throughout the first half as Chivas USA packed the box on the defensive end to keep RSL off the scoreboard. It resulted in plenty of scoring opportunities for the home team before halftime — none of which RSL could finish.
Kyle Beckerman bent a free kick on the frame to force a corner kick in the 22nd minute. Beckerman played it as a short corner and worked the ball into the middle of the box. Yordany Alvarez headed a point-blank shot down the middle, but Chivas goalkeeper Tim Melia defended it perfectly.
Beckerman crossed the ball into the center of the box again in the 28th minute. This time, Saborio got a head on the ball and put it right on frame. But Melia dived low to his right and wrapped up the ball.