Held scoreless for 90 minutes, Sporting K.C.'s attack finally broke through thanks to its hottest player. Salloi worked the ball inside the box and then quickly launched a shot for his 11th goal in his past 14 games.
It was a tough late concession for the Timbers (7-9-3, 24 points), who had led since the 17th minute when Felipe Mora converted a header for his seventh goal of the season. Mora has also been on a roll, with five goals over his last seven games.
Mora's goal was Portland's only on-target shot of the game as the team focused its energies on keeping Sporting K.C. (11-4-5, 38 points) from the equalizer. The Timbers turned in an improved defensive performance following a 6-2 loss to the rival Seattle Sounders on Sunday.
The Timbers have allowed the second-most goals allowed in MLS this season, 36. Sporting Kansas City, meanwhile, ranks second in the league with 36 goals scored.
Though Kansas City held 69.2 percent of the possession and outshot Portland by a 13-8 margin, the home side was lacking in true chances for much of the game.
Diego Valeri had a tremendous chance following a Kansas City turnover in the 75th minute, but the midfielder sent his shot just wide of the net.
Sporting K.C. has lost just once at home this season (5-1-4), while the Timbers have only one away victory (1-6-2).
Defender Graham Zusi played his 307th game with Sporting Kansas City, setting an MLS record for appearances by a player who has spent his entire career with a single team.