Armstrong, the former Under-23 international, featured in the 1-0 win over Rochester Rhinos on Sunday, but it was not enough to avoid elimination in the quarter-final of the play-offs. Rochester had won Friday’s first leg match 2-0.
The Rhinos progressed to the semifinals 2-1 on aggregate.
Greenfield, formerly on the books at Sundowns, scored an own goal as Minnesota Thunder went down 2-0 away at Vancouver Whitecaps on Friday in the first leg of their play-off tie.
Sunday’s return leg saw Greenfield play a full 90 minutes again, but Thunder had to come from 3-1 down to try and salvage the tie. They managed a late comeback, but were eliminated 5-4 on aggregate.