The reinforcements are needed; the Brewers had a "bullpen day" in store against the Cubs, with reliever Tyler Cravy starting in Nelson's place after Nelson was hit in the head by a line drive Thursday and was subsequently shut down. Reed gives Milwaukee coverage for injured right fielder Ryan Braun, who missed three straight starts entering Tuesday with a stiff back. And Rivera provides infield depth while Elian Herrera recovers from a deep thigh bruise sustained in a collision last week at Miller Park.
"It gets us back to, I think, a safe number of players," manager Craig Counsell said. "This past week was a tough week injury-wise for us. Now we've got a normal roster, plus a little extra. We've been short, especially position player-wise. "All the guys we got, I definitely anticipate they'll be some action for them."
Of the callups, only 24-year-old Wagner has appeared previously in the Major Leagues. He made one start against the D-backs on May 31 before returning to Biloxi, where he was 11-5 with a 2.25 ERA in 25 regular-season starts, narrowly winning the Southern League's ERA title over teammate Lopez, who was 12-5 with a 2.26 ERA. Lopez, 22, was named the league's Most Outstanding Pitcher and the Brewers' Minor League Pitcher of the Year.
Wagner and Lopez may get a chance to make a start before the season ends.
"Definitely, one of them will make a start," Counsell said. "We'll see how it works out going forward."
Barrios, 23, and Houser, 22, were acquired in July trades. Barrios came from the Pirates on July 23 for Aramis Ramirez, and he went 6-for-6 in regular-season save opportunities after the trade. Houser was one of four players acquired from the Astros in the Carlos Gomez-Mike Fiers deal, and he went 4-1 with a 2.92 ERA over seven starts with Biloxi.
Both Barrios and Houser were available out of the bullpen on Tuesday.
Reed, 22, posted a .371 on-base percentage in 131 games between Biloxi and Triple-A Colorado Springs while batting .269 with 33 doubles, seven triples, five home runs, 70 RBIs and 26 stolen bases. Rivera, 23, batted .253 between Biloxi and Colorado Springs.
All of those players but Barrios are among Milwaukee's Top 30 Prospects, according to MLBPipeline.com. Lopez is the highest ranked at No. 8.
Wagner and Rivera were already on the 40-man roster, and in adding the other players, the Brewers simply made pre-emptive moves that would have come after the season anyway. They needed to add Houser, Lopez and Reed to the 40-man by mid-November to protect those players from the Rule 5 Draft, and they needed to either add Barrios to the roster or re-sign him to a Minor League contract to avoid him becoming a six-year free agent.
One of the first orders of business for new general manager David Stearns will be sorting out a 40-man roster crunch. Nelson and Blazek must rejoin the roster after the season, and top prospect Orlando Arcia is among the other players who must be added to protect him from the Rule 5 Draft.