Span sprinted diagonally toward left-center field and lunged for the ball near the warning track. He grabbed the ball near his knees, slid on his back and raised his glove in the air, ending the game and securing the Nationals' 6-5 win over the Giants.
Had Span failed to make the catch, Brandon Belt would have scored from second base and tied the game.
"Whew," manager Davey Johnson said. "Heck of a play. I didn't think he was going to get to it. He kind of put it in another gear and then full-out leaped."
"I just put my head down," Span said, "and when I looked up, it seemed like I had gained ground on it. And then that's when I said, 'I'm going to have a chance to reach for it.' And once I caught it, I tried to hold on to it."
Span said it was among the best catches he's ever made. Shortstop Ian Desmond said it's the best grab he's seen during his time with the Nationals, given the circumstances.
"Unbelievable," Desmond said. "He's been amazing all year long. Him being in the American League [before joining the Nationals], we never really got to see him that much. But best center fielder I've ever seen. Never dives. Sometimes he'll slide, but that's the mark of a good center fielder: They don't have to dive. I heard Larry Bowa say that a long time ago."
Pence immediately thought he had tied the game with a hit. He kept his head down as he ran toward first base until the roar of the crowd made him look up.
"I was kind of in a little bit of shock," Pence said. "I thought it was in the gap and it was a long, long way from him. He apparently made a spectacular play. I haven't seen it."
Jayson Werth watched the play develop from his spot in right field. He said he had a bad angle and only saw Span sprint in a straight line and dive.
"It's definitely one way to win a game, that's for sure," Werth said. "You got defensive plays like that and walk-off hits, walk-off homers. There's kind of a parallel there. It's a big play, however you want to look at it. It saved the game."
Jordan Zimmermann and Tyler Clippard were watching the end of the game from the video room in the Nationals' clubhouse. Clippard thought Pence's liner was a catchable ball, until he saw Span was shading to right-center. Zimmermann thought it was an automatic double to the gap until he saw Span.
"All of a sudden, he comes out of nowhere," Zimmermann said. "It was great to see."
The play was especially meaningful for Span considering his struggles at the plate this season. After being brought to Washington during the offseason to be the team's leadoff hitter, Span has only hit .262 this season with a .314 on-base percentage, both well below his career averages of .281 and .350, respectively. Span also has had major issues against left-handed pitching and is batting just .169 against them this year.
"You know what, that's been the main thing that's kept me going. I'm going to be honest with you. My defense," Span said. "If I didn't have that, if I was a DH or a pinch-hitter, I'd have killed myself, probably, two months ago. But whenever I'm struggling at the plate, I try to pick my defense up and try to bring that every day and try to help my team win that way."
While Span has slumped at the plate, he's been nearly perfect in 108 starts in center field. Span and Aaron Hicks of the Twins are the only two center fielders in the Majors with a perfect fielding percentage.
"I think any ball that goes in center field, he's going to catch," Desmond said. "Every time. When he doesn't catch it, it kind of surprises me more than him catching it."
Span put Wednesday's game-saving grab among the top two catches of his six-year Major League career. He said the other was a grab that robbed Adrian Beltre of a home run in 2008, Span's rookie season. But that catch was only in the seventh inning.
"I take pride in my defense," Span said. "Would I like to be hitting .400? Of course. But I love the feeling of taking a hit from somebody or robbing a home run or robbing an extra-base hit. There's no better feeling than being able to do that, especially like tonight."