Though both players ultimately left the field under their own power and maintained consciousness, they came just days after the anniversaries of similar incidents that yielded much worse outcomes.
Red Sox outfielder Tony Conigliaro was hit in the face by a pitch on Aug. 18, 1967, derailing and forever altering his budding career. On Aug. 16, 1920, Indians shortstop Ray Chapman was struck in the face by a pitch and died from his injuries a short time later. He remains the only Major Leaguer to have died from being hit by pitch.
Chapman's horrific incident came years before the use of batting helmets, while Conigliaro's helmet did not have the now-mandatory ear flap that may have partially deflected Niese's offering that hit Heyward.
But Wednesday's plays both provided scares. Heyward immediately fell to the ground in the sixth when a pitch appeared to make contact with that flap and, possibly, Heyward's face. Braves head trainer Jeff Porter and manager Fredi Gonzalez quickly raced out to attend to a visibly distressed Heyward.
"He never lost consciousness," Gonzalez said. "He was talking the whole time when he got hit with the ball. Before they took him to the hospital, he popped his head into the dugout and said, 'Bye,' to some of the guys. I got a chance to talk to him briefly after that."
As for Stassi, he stumbled away from home plate after Scheppers' pitch appeared to graze off his shoulder and mouth. He was promptly met by Astros manager Bo Porter and a trainer who held a towel to Stassi's bleeding face.
"It was a scary situation," Porter said. "I think it hit him in the shoulder and then the face, so that probably lessened the blow. It was frightening. They brought him straight in and took him to the hospital."
The incidents came just three days after the 46-year anniversary of the pitch that hit Conigliaro, who later made an inspirational comeback en route to winning the 1969 Comeback Player of the Year Award. After missing the entire '68 season, Conigliaro returned in '69 to hit .255 with 20 home runs and 82 RBIs in 141 games for the Sox. He improved the following season, crushing a career-best 36 home runs and driving in 116 runs over 146 games.
Though inspirational, Conigliaro's comeback was short-lived as a result of permanent eye damage stemming from the initial injury. He played in just 74 games for the Angels in 1971, and did not play again until attempting a brief comeback with the Red Sox in '75. He played his final big league game on June 12, 1975, at the age of 30.
Former infielder Dickie Thon suffered a similar fate to Conigliaro, having his career permanently altered by a wayward pitch. Following a breakout season and an All-Star appearance in 1983, Thon's '84 campaign was cut short after just five games. He was struck in the face by a fastball that broke the orbital bone around his eye.
Though Thon returned in 1985 and remained in the Majors until '93, he suffered from a lack of depth perception that prevented him from returning to his previous level. He was honored with the second Tony Conigliaro Award in '91 in recognition of his perseverance in the wake of a serious injury.
Other players have been struck in the face by pitches in recent years, with much more favorable outcomes. White Sox captain Paul Konerko has been hit in the face twice in recent years, first in 2010, when he took a Carl Pavano pitch off the jaw. He remained in the game after being checked out by trainers and homered off Pavano in his next at-bat.
Last season, Konerko was again hit in the face, this time by Cubs pitcher Jeff Samardzija on May 18. He left that contest and missed the next two games, before returning and promptly going 14-for-24 (.583) with three home runs and 10 RBIs in his first six games back in the lineup.
Another similar incident took place on the North Side of Chicago in 2011, when then-Cubs outfielder Marlon Byrd was hit in the face just below his eye on a pitch from Alfredo Aceves. Byrd landed on the disabled list and missed more than a month of action due to multiple facial fractures.
Neither Heyward nor Stassi have a timetable for their return yet, but both their teammates and opposing players alike are hoping for quick and full recoveries for the pair. Erik Bedard, Stassi's teammate, was inside the clubhouse when the play unfolded, but it didn't make the situation any less frightening.
"I was inside when I saw it. It wasn't pretty," Bedard said. "I saw [Stassi] when he came back here, and he was a little dazed. I feel for him. You never want to get hit in the face. Hopefully he comes back as soon as he can."
It's a play that every pitcher hopes to avoid, as well. Niese's concern for Heyward's well-being was obvious as he approached home plate immediately after the pitch. Mets catcher John Buck also did his best to console Heyward until Gonzalez and the training staff arrived moments later.
"It was tough. I wanted to elevate a fastball right there, and then it didn't really slip out of my hands, but it kind of just ran in on him," Niese said. "Obviously no intent, but I just felt bad. It's every pitcher and every hitter's worst nightmare. I just hope he's OK."