ST. LOUIS -- - Mike Yastrzemski is comfortable at the plate with the game on the line and he showed it on Wednesday.
Yastrzemski hit a game-tying two-run homer in the ninth inning and Thairo Estrada had the go-ahead single in 10th, and the San Francisco Giants rallied to complete a three-game sweep of the St. Louis Cardinals with an 8-5 victory.
"The kind of thought process is, I've struck out plenty of times in my life, like one more doesn't change anything," Yastrzemski said. "So, there's a calmness in that."
Yastrzemski's shot, which came on a 2-2 count with two outs in the ninth inning off Cardinals closer Giovanny Gallegos, made it 5-5. The Cardinals extended their skid to five games and fell to a season-worst 15 games under .500. It was the third blown save of the season for Gallegos.
"We just don't execute," Cardinals third baseman Nolan Arenado said. "This has nothing to do with the coaches, it has to do with the players and as players we don't execute."
The late offensive spark lifted the Giants' winning streak to four games.
"Nobody we'd rather have up in those kind of moments because his heartbeat is so slow," Giants manager Gabe Kapler said of Yastrzemski. "You know he's going to be totally prepared for the moment. Nothing's going to be too big for him and he's going to get a good swing off. Not always going to end like that, but obviously we've seen him with some pretty big home runs over the last couple of years."
"We just have to play better," Cardinals catcher Andrew Knizner said. "There's a lot of things that don't go our way, but you usually can fight through that stuff when you're playing good baseball."
Tommy Edman's second career grand slam gave the Cardinals a 4-2 lead in the second inning and Jordan Walker added an RBI single in the third as St. Louis chased Giants starter Anthony DeSclafani after just three innings.
But the San Francisco bullpen shut the door from there as five relievers combined for seven scoreless innings. Tyler Rogers (1-4) got the win with a perfect ninth inning and Camilo Doval earned his 18th save in 19 opportunities.
"Those guys are a grindy group and I have faith in every single one of them," Yastrzemski said. "So, it's really cool when they have that moment to kind of step up and do what they do. And it's not easy for them to mentally stay in when we go down early like that and to keep us in the game. That's probably the biggest thing that allows us to come back there."
Cardinals starter Jordan Montgomery gave up three runs in 6 1/3 innings, allowed seven hits, walked two and struck out seven.
Highly touted rookie Luis Matos made his debut for the Giants in center and singled in his first major league at-bat as part of a two-run first inning. Estrada and Patrick Bailey had RBI singles during the rally.
"I had a little bit of nerves, just a little bit not that much, but at the same time since I saw the team in spring training that kind of helped me get more comfortable," Matos said through an interpreter.
Yastrzemski ended Montgomery's day with an RBI single in the seventh to make it 5-3 and start the Giants rally.
San Francisco recalled Matos and INF David Villar from Triple-A Sacramento. Matos, 21, was hitting .398 with a 1.120 OPS and seven home runs in 24 games at Sacramento. He went 1 for 3 before being lifted for pinch hitter Michael Conforto in the seventh. RHP Keaton Winn was optioned to Sacramento.
Giants: OF Mitch Haniger (fractured right forearm) was placed on the 10-day Injured List. ... INF J.D. Davis (right ankle sprain) was not in the lineup after being removed from Tuesday's game in the third inning.
Cardinals: LHP Packy Naughton (left forearm strain) got a second opinion and is deciding on treatment options.
Giants: Neither team has announced a starter as the Giants start a three-game series at the rival Los Angeles Dodgers on Friday.
Cardinals: RHP Miles Mikolas (4-3, 4.02 ERA) kicks off a three-game series on Friday night at New York against the Mets. Mikolas is 1-1 with a 1.64 ERA in four career appearances (three starts) against the Mets.