The 36-year-old from Northern Ireland arrived at TPC Sawgrass near Jacksonville on the eve of the event after withdrawing from last week's Arnold Palmer Championship at Bay Hill with only a month until he seeks a repeat crown at the Masters.
"It's better than it was," McIlroy said. "I hit up until a 6-iron on the range there, and it felt OK.
"We'll see. I'm taking it sort of hour by hour, but it feels better. I couldn't stand to address the ball on Saturday morning on the range at Bay Hill, and it's obviously better than that.
"So, yeah, probably a game-time decision, but all indications are pointing in the right direction. So, hopefully, good night tonight, the drugs are working wonders and then just keep it going from there."
Second-ranked McIlroy saw a physio in West Palm Beach last Saturday after pulling out at Bay Hill and said he has improved ever since. He plans to test himself with a driver in Thursday's opening round but said he is not in pain.
"I wouldn't even call it pain. I would say just more like sensitivity," he said. "Just hitting balls there for a little bit, just feel like my muscles around the area just getting a little bit, like, fatigued. Right adductor started to cramp a little bit. But it's fine. It's expected.
"I'd like to think that the sensitivity will go down as time goes on."
McIlroy, a five-time major winner who completed a career Grand Slam with last year's win at Augusta National, is not worried about adding to his woes by playing this week.
"What I've been told, obviously I'll listen to the professionals, but there's nothing that I can do that's going to harm that," he said. "I don't think it's something where if I play I'm at risk of doing any damage."
PGA Tour chief executive officer Brian Rolapp spoke about planned future tour priorities, including a January to September schedule of 21-26 events, more 120-player events and fewer low-field no-cut tournaments, a marquee opener, more major markets, possible relegation and more playoff drama, possibly including match play.
"We're aiming to go create a more cohesive schedule with a simpler point system, one where the best players compete against one another more frequently," Rolapp said.
McIlroy approved of the ideas.
"It's all pretty positive," McIlroy said. "I think what he said today, it's obviously a really good direction of where the tour should be going."