But the N.B.C.A. ballot, according to two people familiar with voting procedures, only asks coaches to submit one name, which could help explain why there were no votes for Stevens — who has won raves leaguewide for guiding the Celtics to within one of the Eastern Conference finals entering Wednesday night’s Game 5 against Philadelphia despite the absence of his injured stars Kyrie Irving and Gordon Hayward.

According to the N.B.C.A., seven other coaches received votes in addition to Casey: Philadelphia’s Brett Brown, Houston’s Mike D’Antoni, Indiana’s Nate McMillan, San Antonio’s Gregg Popovich, Utah’s Quin Snyder, Portland’s Terry Stotts and the Los Angeles Clippers’ Doc Rivers.

Those results sparked a social media outcry Wednesday, not necessarily because Casey won after leading Toronto to a franchise-record 59 wins and the best record in the Eastern Conference, but because Stevens was completely overlooked.

The N.B.A. relies almost exclusively on members of the news media in balloting for its annual awards because it believes that they comprise the voting body that will be the most thorough in its research — and the least likely to let personal biases influence their selections. The league’s annual Executive of the Year award is its only season-ending honor in which each team’s top basketball executive votes as opposed to the news media; the award has long generated whispers in league circles about certain candidates struggling for votes because of frosty relationships with their peers.

But for all the praise he has received at a young age for his play-calling and impact from the sideline, Stevens, 41, is not at all regarded as the sort of self-promoter who would theoretically inspire jealousy or turn off fellow coaches.