James, who had been sidelined for nearly two weeks after stepping on rookie teammate Cedi Osman's foot on the second day of training camp, tallied 17 points in the loss.
"Well, me personally, tonight I was off," James said. "I could feel it. It's just my first action since the Finals and my timing was a little off and turnovers I think just trickled down to everybody, so I made everyone's timing off."
The challenge was ultimately twofold for James: get back his conditioning and rhythm after being sidelined for nearly two weeks, and acclimate to a handful of new teammates, including a completely overhauled starting lineup compared with what he played with en route to three trips to the NBA Finals in the past three years.
James made the first shot he took -- a long pull-up jumper with Bulls center Robin Lopez guarding him on a switch at the top of the key -- and generally scored the way he has the past 14 years of his career -- including stuffing back-to-back dunks in the first quarter.
It was his ball control that was lacking.
James committed seven turnovers -- all in the first half -- and looked like a guy who spent the past two weeks rehabbing while the players around him were sharpening their games.
James was self-deprecating about his poor showing. In the postgame locker room, he tried to throw a towel into a bin before speaking to the media and wound up hitting Cavs director of communications B.J. Evans with it by accident. "My passing was off all night," James said. "Sorry, B.J."
James tweaked his left ankle in the first quarter after losing the ball out of bounds following a spin move to get to the basket, but kept playing after walking it off during a break in play.
"I'm pushing through it right now," James said. "I just wanted to try and test my foot, test my ankle to see how I would come out tonight. So, obviously tonight and tomorrow morning it's going to be a telltale sign of how I came out tonight. I'm still fresh from the game so it's OK now but you never know when you wake up the next morning how it can flare up or if it can stiffen on you. So, I'll know more about it tomorrow but I definitely wanted to test it tonight knowing that at least if I tested it tonight I have a week until the regular season started if I don't play in the game on Friday."
James reiterated that he's still not 100 percent but said he was motivated to return to the lineup to gauge where he is at.
"I got to play at some point so I wanted to test it out and understand that and see how I feel," he said.
With that said, James' 17 points still led the Cavs and he shot 8-for-13 from the floor with 5 rebounds, 3 assists, 2 steals and a block.
"He hasn't played in I don't know how long," Cavs coach Tyronn Lue said. "Of course his rhythm is going to be off. His passing, timing. That's just part of the game. But I'm not worried about Bron. He'll be OK. Tonight is his first night playing in a long time. He'll get his rhythm. I'm not too worried about that."
Cleveland had little continuity as a group, however, and the Cavaliers could often be seen pointing and gesturing to one another in the middle of plays to direct people where to go.
"I don't think we'll be the team we want to be in a week," James said when asked about the season opener against Boston. "It's going to be (a process) for the whole season. We're going to have changes, we're going to make changes, we're going to become a better team as the games go on so the team opening night will not be the team that we know we can be. We're going to be as good as we can be up to this point. We've only practiced for two weeks and you play on the third week, that's not like a lot of time to prepare, especially when you have so many new guys playing here."
The Cavs finish off the preseason Friday on the road against the Orlando Magic and will look to avoid an 0-5 exhibition record.