"It's a bad break. He's a fantastic player and character. It's a major blow for the lad, his club and us," said Ireland manager Martin O'Neill, who confirmed Coleman had gone to hospital.
"Seamus is a major blow. At the end of it all, the most important thing is Seamus's health."
"He's having the season of a lifetime at club level. He's a big player for us, a great captain and a great character."
Wales held out for a draw despite their numerical disadvantage, but they remain four points below Ireland and new group leaders Serbia, who came from behind to win 3-1 in Georgia.
Chris Coleman's side travel to Belgrade for their next qualifier in June and must do so without talisman Gareth Bale after he picked up a booking that triggered a one-game ban.
It was a fourth successive draw for Wales, surprise semi-finalists at Euro 2016. They have not beaten Ireland since February 1992.
Things look rosier for the Irish, who host Austria in their next Group D assignment, but the thoughts of all who drifted out of the Aviva Stadium were with Seamus Coleman.
"I have my fingers crossed for Seamus Coleman. He is the most important thing tonight," Wales manager Chris Coleman told Sky Sports.
"Neil (Taylor) is in the dressing room, he's despondent. He's had a serious injury himself."
It was also a poignant night for Ireland winger James McClean following the sudden death of his close friend Ryan McBride, the Derry City captain, at the age of 27 last Sunday.
The West Bromwich Albion player wore the number five shirt in McBride's honour and was named man of the match after an enterprising and committed display.
While Chris Coleman was able to revert to his first-choice starting XI, Ireland's injury problems were exacerbated when James McCarthy had to withdraw from the starting XI just before kick-off.
The Everton midfielder had been passed fit following a hamstring injury, but David Meyler ended up taking his place, increasing the number of changes from November's 1-0 win in Austria to six.
Ireland were content to let Wales have the ball and Bale found himself dropping deeper and deeper in an attempt to influence proceedings.
He produced one glorious, booming 40-yard pass to Taylor, who was unable to bring the ball under control, but otherwise the Real Madrid star looked off his game.
Teed up by Aaron Ramsey, who had shrugged Jeff Hendrick off the ball, his touch betrayed him and when he took aim from range shortly before half-time, the ball skidded harmlessly wide.
The interval arrived without either goalkeeper having been worked, but that soon changed as Wales, who sent on Sam Vokes for Hal Robson-Kanu, looked to raise the tempo.
Ireland goalkeeper Darren Randolph was obliged to field efforts from Bale and Ramsey, while Bale fizzed a shot narrowly wide from 25 yards on the left.
Ireland offered no kind of threat until the hour, Richard Keogh diverting a Glenn Whelan corner off-target with his shoulder and Shane Long volleying wide.
The booking that rules Bale out of Wales's trip to Serbia occurred in the 68th minute after he caught John O'Shea as he slid in to attack Chris Gunter's cross.
Asked by an Irish journalist if Bale had been lucky to avoid a second booking for a high foot on James McClean, Chris Coleman said: "Do you think one or two of yours were lucky to stay on the pitch?
"Because it was a little bit of both. Your boys were not coming off there with halos on their head. It was going on all through the game.
"It was a typical British game of football. There were one or two complaints from our boys, that your boys were a little bit late here and there.
"And some of our boys were as well. I'm not complaining. That's football."
Italian referee Nicola Rizzoli reached for his pocket again a minute later, but this time the card was red after Taylor's ugly challenge left Coleman in a crumpled heap.
Ireland's fans roared their disapproval when Bale avoided a second yellow for a high challenge on McClean.
They were almost given extra reason to rue Rizzoli's leniency seconds later, but after surging from deep, Bale's long-range shot flashed inches wide.