Every game has a turning point, when one team takes a big leap toward victory, whether it's a towering home run, a squeeze bunt, a bases-loaded strikeout or a run-saving catch.
Thanks to a metric called win expectancy, we can attach numbers to these swings in fortune. Win expectancy, expressed as a percentage, shows a team's chances of victory at a particular point in time. This is based on historical data showing how clubs have fared in different situations, based on factors such as the score, the inning, how many outs there are and which bases are occupied.
Using win expectancy as a guide, here is a look at three plays that served as turning points in Sunday's games:
Altherr brings the Phillies back Game: Nationals at Phillies
Situation: Philadelphia trailed, 5-2, in the bottom of the eighth when Cesar Hernandez and Daniel Nava hit back-to-back singles off Washington's Matt Grace. After Odubel Herrera flied out, Altherr came off the bench to pinch-hit with two outs. Nationals manager Dusty Baker replaced Grace with right-hander Matt Albers.
Result: Altherr greeted Albers' first pitch with a mighty swing, sending a slider high and deep to the left-center field seats for a three-run, game-tying home run. The clubs remained knotted at 5 until the bottom of the 10th, when Freddy Galvis sent the Philly faithful home happy with a bases-loaded walk-off sacrifice fly to cap the come-from-behind 6-5 victory.
Win expectancy for Phillies: +44.6 percentage points (8.0% to 52.6%)
Facts to know
• The Phillies' win expectancy was hovering at just 5.6 percent when their offense dug in for the bottom of the eighth.
• Altherr's blast -- just the 13th of his young career -- was a no-doubter, traveling a projected 412 feet as measured by Statcast™. That marks the second-longest homer of Altherr's big league tenure, and his longest since coming back from the wrist surgery he underwent early last year.
They said it: Phillies manager Pete Mackanin on Altherr's retooled swing: "He's always had too long of a swing. He had a little bit of a contorted setup in the box. He just shortened everything up. His bat is on his shoulder. He takes it from Point A to Point C and eliminates Point B. He's direct to the ball, and he's getting good results."
Pham-tastic blast Game: Cardinals at Braves
Situation: In a Sunday getaway game, the Cardinals refused to leave Atlanta without a sweep in hand. St. Louis raced out to an early 4-0 lead before the Braves battled back, tying the game at 4-4 in the eighth inning and eventually sending it to extras. Atlanta stranded seven runners during extra innings alone, keeping the Cardinals alive until the top of the 14th. Magneuris Sierra reached on an error by Braves second baseman Jace Peterson, bringing Tommy Pham to the plate with one on and one out against Braves reliever Josh Collmenter.
Result: Pham, who had already clubbed a home run in the third, crushed a 1-0 cutter from Collmenter into the left-field seats for a no-doubt, two-run go-ahead homer in the 14th for the Redbirds. Cardinals reliever Kevin Siegrist came on in the bottom of the frame and twirled a perfect inning, sealing a hard-earned victory and sweep for St. Louis.
Win expectancy for Cardinals: +41.8 percentage points (50.1% to 91.9%)
Facts to know
• Pham saved the Cardinals' hardest hit of the year for one of the team's biggest moments. No other Cardinal hitter has topped Pham's 110.1 mph exit velocity on his go-ahead in 2017. In fact, St. Louis was one of just three Major League clubs entering Sunday that had not hit at least one home run with an exit velocity of at least 110 mph, until Pham put it on the board with one big swing.
• Pham was appearing in just his third game of the season for St. Louis, but he makes the most of the rare opportunities he gets to swing the bat. The outfielder is now averaging a 94.7 mph exit velocity on batted balls in 2017 after his two-homer day Sunday, the highest of any Cardinals hitter with at least five batted balls tracked by Statcast™. That kind of power is not a fluke for Pham, either; he ranked second to Matt Holliday among Cardinals hitters last year with an average exit velocity of 92 mph.
They said it: Pham on stepping up in extra innings: "I was joking around [in the dugout], saying, 'We don't get paid for overtime, so let's go.'
"I was pumped to come through. It's not like you can keep sending guys out to pitch in extras. Our bullpen is doing the job for us. They're holding the game. We have to pick them up."
Valencia brings Seattle back Game: Rangers at Mariners
Situation: The Mariners looked to be on the verge of a series loss to the rival Rangers as they trailed Texas, 3-0, entering the bottom of the seventh. But Seattle remained patient at the plate. Kyle Seager and Taylor Motter drew back-to-back walks to open the frame, and after a fielder's choice wiped out Motter at second, Jarrod Dyson and Jean Segura brought in the Mariners' first run with another pair of walks.
Rangers manager Jeff Banister replaced Jose Leclerc with left-hander Alex Claudio. Mariners manager Scott Servais countered by bringing in the right-handed Danny Valencia off the Mariners' bench to pinch-hit for Ben Gamel with two outs and the bases packed.
Result: Valencia worked the count to 2-1 before fighting off an 87 mph sinker from Claudio for a broken-bat base hit up the middle. Guillermo Heredia and Dyson came around to score and tie the game up at three. Seager launched a solo homer for Seattle the next inning to cap off a 4-3 series-clinching victory.
Win expectancy for Mariners: +33 percentage points (25.7% to 58.7%)
Facts to know
• Valencia had hit just .140 (6-for-43) as a pinch-hitter over his eight-year career before his clutch two-run single off the bench Sunday.
• Valencia's single improved the Mariners as a team to 9-for-25 (.360) against sinkers in '17, ranking them among the five best teams in baseball against that pitch.
They said it: Rangers manager Jeff Banister on having the left-hander Claudio face the right-handed Valencia: "Obviously make a switch there, bring Claudio in, a guy that's maybe a little calmer in that situation. I felt like he made a good pitch to Valencia, but he got enough of the bat on it to lift it up for a soft liner to center field."
Matt Kelly is a reporter for MLB.com based in New York. Follow him on Twitter at @mattkellyMLB. This story was not subject to the approval of Major League Baseball or its clubs.