ESPN.com's Adrian Wojnarowski first reported the news, which the Knicks later confirmed (h/t ESPN's Alan Hahn).
Wojnarowski added the Knicks are "planning to contact" former Golden State Warriors head coach Mark Jackson, former Cleveland Cavaliers head coach David Blatt and former Memphis Grizzlies boss David Fizdale as they ramp up their search for Hornacek's successor.
The Knicks hired Hornacek in June 2016 after firing Derek Fisher during the 2015-16 season. He was a surprise choice since Phil Jackson, who was the team's president at the time, intended to hire someone who understood his philosophies, per Newsday's Al Iannazzone:
"Only people I probably know will be in the interview process. I will reach out to make connections to some people. But I've been in this position, in the NBA over 50 years, and I've seen a lot of situations where coaches end up coming in without simpatico with the general manager, and those things don't work well. So someone who has compatibility with what I do as a leader would have to be in sync with what we do."
Following Jackson's departure prior to the 2017-18 season, the Knicks reshaped their roster by trading Carmelo Anthony to the Oklahoma City Thunder. Kristaps Porzingis took the reins as New York's face of the franchise upon Anthony's departure, but his season came to a premature end when he tore his ACL during a Feb. 6 game against the Milwaukee Bucks.
Even before Porzingis went down, the Knicks were a mess. They finished 29-53 this season and went 60-104 during Hornacek's two years at the helm.
Prior to joining the Knicks, Hornacek spent two-and-a-half seasons as the Phoenix Suns' head coach before he got canned midway through the 2015-16 season. He may need to sit out for a bit to find a job with young talent on the rise to avoid another disastrous situation like New York's.
The Knicks, meanwhile, must now go back to the drawing board to find a coach who can help drag them back to respectability. That won't be easy, especially with Porzingis likely to miss time next season as he recovers from ACL surgery.