Salt River (14-12) appears on a collision course with West Division-leading Peoria Javelinas (17-10), who own the Fall League's top record.
Rienzo (1-1) gave up two runs on three hits, including an RBI single by catcher Cory Brownsten (Braves) in the second. The 24-year-old right-hander, a native of Brazil, pitched around three walks, throwing 47 of 73 pitches for strikes.
Rienzo, who finished the Minor League season at Triple-A Charlotte, lowered his ERA to 4.74 through six AFL outings. He could make a seventh before the season is over.
His counterpart, Braves prospect Zeke Spruill, was charged with three runs -- two earned -- on three hits, including a two-run double by designated hitter Jason Martinson (Nationals), over four innings. Spruill (1-2) and five relievers were undone by poor defense. The Dogs committed six errors, including one by each member of the infield.
The miscues led to four runs, two of which scored on an errant throw by Brownsten as Brian Goodwin (Nationals) and Tyler Bortnick (D-backs) attempted a double-steal.
Blue Jays prospect and Midwest League MVP Kevin Pillar went 3-for-5 with a pair of RBIs and two runs scored for the Rafters, who got two hits from Rockies No. 19 prospect Corey Dickerson.
Marlins top prospect Christian Yelich delivered a two-run double for Phoenix.
Andrew Pentis is a contributor to MLB.com and writes the Prospective Blog. Follow him on Twitter at AndrewMiLB. This story was not subject to the approval of Major League Baseball or its clubs.