On the offensive end, O'Brien knocked in all of the Aces' runs with a sixth-inning grand slam.
The outfielder has been in Reno all season and has put up impressive numbers for the Aces. Tuesday's slam marked his 15th homer of the season, which put him in a tie for first with two players in the Pacific Coast League. He also has 57 RBIs, good for third in the PCL.
While he's experiencing somewhat of a mini-slump -- his average has fallen from .352 to .297 since May 27 -- O'Brien has two homers and five RBIs in his past four contests.
The rest of the 10 best performances from top Minor Leaguers
• Cubs No. 13 prospect Dan Vogelbach launched a three-run HR to put the North up for good in the Southern League All-Star Game. His blast came off of Reds No. 1 prospect Robert Stephenson, who surrendered four runs (two earned) in the second inning. Vogelbach's dinger made the score 3-0 and helped open the offensive floodgates in the North's 9-0 victory. Vogelbach has been in somewhat of a slump as of late, but he had a 2-for-5 night with three RBIs in his final game of the first half for Double-A Tennessee on Sunday. The first baseman is hitting .285/.400/.425 with four homers and 31 RBIs this season.
• Indians No. 27 prospect Nellie Rodriguez outlasted Astros No. 12 prospect A.J. Reed for the Class A Advanced Home Run Derby crown. The pair had a close 5-4 battle in the final round, but Rodriguez squeaked by. While Rodriguez has been productive this season -- nine homers, 54 RBIs -- his numbers aren't quite as impressive as Reed's performance this year. The JetHawks' first baseman has clobbered 18 home runs -- second in the Minors -- and has 65 RBIs.
• Nationals prospect Mariano Rivera made his professional debut for Class A Short Season Auburn on Tuesday night. The son of Mariano Rivera, the all-time saves leader and Yankees legend, appeared in relief as Metallica's "Enter Sandman" blared over the sound system during his warm up. Rivera retired three hitters in the bottom of the sixth inning before giving up two singles to begin the bottom of the seventh. But State College's rally didn't materialize as Rivera proceeded to strike out three straight Spikes. With that, the fourth-round Draft pick was finished for the night, tallying four strikeouts -- all of the swinging variety -- in all.
• Orioles No. 3 prospect Christian Walker went 3-for-6 with a double, homer and an RBI for Triple-A Norfolk. Tuesday's torching came against Columbus, a team that would rather not see Walker again. The first baseman has a .590 on-base percentage in five games against the Clippers this year. Overall, he's hitting .265/.328/.373 with three home runs and 23 RBIs.
• Padres No. 15 prospect Colin Rea has tossed 15 straight shutout innings for Double-A San Antonio. The 6-foot-5 right-hander scattered three hits and struck out two in seven shutout innings Tuesday and hasn't allowed a run since May 18. He suffered a back injury that day, but returned on June 13 and has been an absolute force since. On the season, he's 2-2 with a 1.06 ERA in 11 starts.
• Rangers No. 3 prospect (No. 45 overall) Nomar Mazara ripped his seventh homer of the month for Double-A Frisco. The dinger -- his ninth of the year -- came as part of a 1-for-3 night and Mazara has now hit in three straight games after going three games without a hit. He's hitting .285/.368/.462 with nine homers and 36 RBIs this year.
• Twins No. 12 prospect Adam Brett Walker took a break from shelling Double-A pitchers and instead ripped 13 home runs to win the Southern League Home Run Derby. The title of "Derby Champion" isn't new to the Minor League home-run leader (19). He outslugged several other prospects for the Florida State League Derby title last summer. The 23-year-old is currently hitting .270/.325/.585 with 17 doubles, two triples and 59 RBIs and is well on his way to setting new career high marks in homers (27), RBIs (109), doubles (31) and slugging percentage (.526).
• White Sox No. 1 prospect (No. 64 overall) Tim Anderson turned 22 years old on Tuesday and capped off the day by winning the Southern League All-Star Game MVP award in his home state. The Tuscaloosa native went 2-for-3 with a double, triple and an RBI out of the leadoff spot as the North beat the South, 9-0, in Montgomery, Ala. His big night came amidst a hot streak as he's 8-for-13 in his past three games for Double-A Birmingham. The shortstop is currently hitting .313/.337/.414 with one dinger, 28 RBIs and 23 stolen bases this season.