The Ecuadorian forward inspired RSL to a 3-2 come-from-behind victory at Chicago Fire with a late brace to help the Utah club extend their unbeaten run to nine matches.
RSL trailed when Mike Magee and Juan Luis Anangono had scored by the half-hour mark but Plata pulled a goal back in the 72nd minute from inside the area before Alvaro Saborio tied it up in the 90th minute.
RSL then went after a winner and it came in stoppage time when Plata converted a neat cross from Saborio at the back post to give his side a record of four wins and five draws from their opening nine fixtures.
Plata now has five goals this season - his highest season tally in four years in MLS - and joins teammate Nick Rimando on the MLS Player of the Week list after the goalkeeper was rewarded for his defensive efforts in Week 1 and Week 7.
2014 MLS Player of the Week
Week 9: Joao Plata (Real Salt Lake) Week 8: Bradley Wright-Phillips (New York Red Bulls) Week 7: Nick Rimando (Real Salt Lake) Week 6: Clint Dempsey (Seattle Sounders) Week 5: Clint Dempsey (Seattle Sounders) Week 4: Graham Zusi (Sporting Kansas City) Week 3: Bernardo Añor (Columbus Crew) Week 2: Jermain Defoe (Toronto FC) Week 1: Nick Rimando (Real Salt Lake)
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