Phoenix Suns center Deandre Ayton has been suspended 25 games after he tested positive for a diuretic, the NBA announced Thursday.

The suspension comes one day after Ayton, the top overall pick in the 2018 draft, finished with 18 points and 11 rebounds in an impressive 124-95 blowout win over the Sacramento Kings in Phoenix’s season opener.

Ayton, 21, will begin serving his suspension Friday night against the Denver Nuggets, and will be sidelined until a Dec. 17 game against the Los Angeles Clippers. Given that his suspension is without pay, Ayton will forfeit more than $2.1 million of his $9.6 million salary.

“I want to apologize to my family, the entire Suns organization, my teammates, partners, our fans and the Phoenix community,” Ayton said in a statement, adding that he plans to take the suspension to arbitration with the help of the National Basketball Players Association. “This was an unintentional mistake and unfortunately I put something in my body that I was completely unaware of. I do understand the unfortunate impact that this has on so many others, and for that I am deeply sorry. I’m extremely disappointed that I’ve let my team down.”

The NBA’s comprehensive anti-drug program includes random testing for marijuana, steroids and drugs of abuse. A positive test triggers a range of consequences — from a warning or a lifetime ban — depending on the substance.

Any player testing positive test for a diuretic, which can potentially mask a drug test’s results, shall be, according to the program, “deemed to have tested positive for a steroid or performance-enhancing drug and shall suffer the applicable consequences.” Because the league issues a 25-game suspension for first-time violations involving steroids and performance-enhancing drugs, that’s what Ayton received.

Phoenix selected the 7-foot-1 Ayton, who spent one year at the University of Arizona, at the top of a talented draft class. That decision drew some second-guessing last season, as Dallas Mavericks guard Luka Doncic ran away with rookie of the year honors and Atlanta Hawks guard Trae Young finished second. Even so, Ayton averaged 16.3 points and 10.3 rebounds per game as a rookie and is viewed as a central piece of a young Suns nucleus that also includes guard Devin Booker.

Ayton’s extended absence will be a major blow to the Suns, who are seeking to generate some positive momentum after nine straight lottery trips. Following a 19-win season last year, Phoenix named James Jones as its full-time GM, hired Monty Williams as head coach and acquired a host of veteran players, including Ricky Rubio, Aron Baynes and Dario Saric. Baynes, a 32-year-old center who spent the past two seasons with the Boston Celtics, will likely move into a starting role until Ayton’s return.

The Suns issued a statement Thursday saying that Jones and Williams were “disappointed” in Ayton’s actions.

“This does not uphold the standards and principles we have set for the team,” Jones said. “Deandre has expressed his deepest remorse. While he is suspended we remain committed to his growth and development on and off the court. His actions are not taken lightly, and we are committed to ensuring that Deandre understands the profound impact it has had on the team, organization, and Suns community.”

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