Nationals pitching coach Steve McCatty was taken to the hospital before the start of today's game, a team spokesman confirmed.
McCatty, 59, was not feeling well and will not be present for today's series finale against the Mets.
The Nationals are not releasing any more information at this time and say they will provide an update on McCatty's health later.
McCatty is in his fifth season as the Nationals' pitching coach. This is his 18th season as a professional pitching coach, following a nine-year big league playing career.
News of McCatty's absence was first reported by MASN's Julie Alexandria on today's game broadcast.
Update: The Nats took a 3-0 lead in the second thanks to four hits in a five-batter span.
Ian Desmond's double was followed by singles from Denard Span and Wilson Ramos, the latter of which brought in Desmond with the game's first run.
Two batters later, after Taylor Jordan laid down a perfect sac bunt with two strikes on him, Bryce Harper dropped a single into left, scoring two more runs to make it 3-0.
The Nats went 3-for-3 with runners in scoring position that inning, a rarity for a team that has been awful in such situations lately.
Span is now batting .333/.333/.555 when hitting in the No. 7 spot in the lineup (27 plate appearances), compared to a .253/.312/.342 line when leading off.
Jordan, meanwhile, has worked three perfect innings, striking out three. He's thrown just 37 pitches and has looked really sharp today, dialing his two-seam fastball up to the 95 mph range and showing an impressive changeup.