Heyward missed the ball -- it popped out of his glove when his glove knocked against the wall -- and Fontenot ended up standing on third with a triple. Atlanta's rookie right fielder ended up on the ground.
Braves manager Bobby Cox and trainer Jeff Porter hesitated before coming out of the dugout, clearly expecting that Heyward would bounce to his feet and assume his defensive position. But Heyward couldn't, and it took several minutes and some discussion with Porter before the right fielder stood back up.
"I was dizzy and light-headed before I got up," Heyward said. "I had to take my time."
Heyward finished the game, but he admitted afterward that he did so at less than full health.
"For the next five innings, my eyes, it felt like it was hard to keep them open," he said. "I am kind of sore right now. My jaw is kind of sore. It was tough, but I had to hang in there."
Heyward expects to start Monday's Game 4, though he'll be evaluated on Monday afternoon before any final decision is made.
While the Atlanta outfielder spends the next 24 hours recovering from hitting a wall, he may have recently hit another wall -- this one figuratively, of course. Hitting out of the lineup's second spot, Heyward is 0-for-12 in the NLDS and has struck out seven times. Three of those strikeouts came on Sunday, including one to lead off the ninth.
This marks the first time since Heyward returned from a thumb injury on July 15 that he has gone hitless in three straight games.
Heyward was asked if the Giants -- against whom he went 6-for-23 during the regular season -- were pitching him any differently this series.
"Not too different," he answered. "They've pitched well. [Giants starter Jonathan] Sanchez is tough against lefties, and he threw a great game."
Heyward's offensive struggles go back a bit further than Thursday. Since Sept. 22, the outfielder has just six hits in 50 at-bats and has struck out 17 times. Only one of his six hits has gone for extra bases.
Jenifer Langosch is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.