It proved to be a smart move.
St. Louis, which had lost three of its previous four, moved two games behind first-place Milwaukee in the NL Central. The Brewers had a two-game winning streak snapped.
Wong, who entered the contest mired in a 6 for 36 skid, went 3 for 5. He slammed a bases-loaded single to trigger a five-run outburst in the second inning that put St. Louis ahead to stay 6-1. He also hit a solo homer in the first.
"That worked out fine for all of us," Matheny said of the late pre-game move. "It was nice to see him bounce back. With a young player, when he has a couple of rough days, you wonder, `can he leave it behind and go back to having a nice approach.' He jumped right in and had some big at-bats."
Wong was 2 for 3 in his career against Brewers starter Kyle Lohse, a key factor in Matheny leaving him in the lineup.
Wong, who entered the game hitless in his previous eight at-bats, spent some extra time studying his approaches at the plate following Friday's 7-4 loss to Milwaukee.
"I knew the reason I was striking out as soon as the game finished yesterday," Wong said. "I was swinging way too hard trying to do way too much."
Masterson (1-0) gave up five runs on seven hits over six innings. He was acquired from Cleveland on Wednesday for minor league outfielder James Ramsey.
"There was a little rust out there," Masterson said. "But with that intense offense that we had, and some solid defense, that makes it fun to be out there."
Lohse (11-6) took the loss. Lohse, who pitched for the Cardinals from 2008-12, gave up nine runs on nine hits over four innings. He struck out two and walked three. Lohse gave up eight earned runs in a 15-5 loss at Pittsburgh on June 6.
"It was just a rough one," Lohse said. "I just left too many balls out over the plate."
St. Louis closer Trevor Rosenthal recorded his 33rd save in 37 opportunities. He allowed a leadoff double to Jean Segura. Rosenthal then appeared to hit Elian Herrera with a pitch, but the call was overturned by a challenge. Rosenthal then got Herrera to ground out. He struck out Carlos Gomez and Gerardo Parra to end the game.
Former US Navy SEAL Marcus Luttrell threw out the first pitch. Luttrell was awarded the Navy Cross and Purple Heart for his actions in June 2005 as part of Operation Red Wings. He wrote the best-selling novel, The Lone Survivor, which has been turned into a movie starring Mark Wahlberg.
Cardinals: OF Jon Jay missed his fourth successive game with a sore wrist suffered on a check swing July 29 at San Diego. He says the wrist is improving and he could return to the starting lineup as early as Tuesday against Boston.
Brewers: RHP Jimmy Nelson, who was scratched from Saturday's start due to a blister on his finger, will start on Tuesday against San Francisco.
John Lackey (11-7, 3.60) will make his St. Louis debut on Sunday in the final game of the three-game series. He will be opposed by Matt Garza (7-7, 3.74). The Cardinals obtained Lackey on Thursday from Boston in exchange for OF Allen Craig and RHP Joe Kelly.
The Brewers have been in first place in the NL Central every day since April 5, a streak covering 121 successive days. They lost two of their first three games to open the season and spent two days in third place and one each in second and fourth before taking over the top spot.