RSL is taking its undefeated record on the road as it faces a Philadelphia team looking to end a three-game winless stretch.
The Union traded last season's top scorer, Jack McInerney, to Montreal last week in exchange for local product Andrew Wenger, and the Lancaster-born forward could make his first appearance for the Union against last season's Western Conference champion.
Philadelphia is fifth in the Eastern Conference with a 1-1-3 record, but hasn't tasted victory since its 1-0 win over New England on March 15.
Salt Lake is 2-0-3, second in the West, one of just two undefeated sides left in the league. RSL has given up just four goals, the second-stingiest defense in the West, and tied with three Eastern Conference teams for the second-best defense in the league.
In six games all-time, Philadelphia has never beaten RSL, with the Utah side winning twice and four draws shared between the two.