CHICAGO - Progressions for Chase Utley are difficult to measure, because the second baseman insists on privacy and has done so much of his work to strengthen his chronically injured knees behind closed doors or in Arizona.

So take this as a positive: Utley took ground balls Wednesday for the first time in nearly a month. Then he woke up Thursday and decided he felt so good he wanted to run. And once batting practice started later in the afternoon, he was at second, taking more grounders.

"Over the past year or so, I know the pain threshold I can play at," Utley said. "And right now I'm in the good zone."

When Utley rejoined the team May 5, he said his next step was increasing his infield workload. But it took until Wednesday for Utley to reach that point.

Why?

"I'm trying to get to a point where when we start going for it, I feel pretty comfortable," Utley said. "I've realized over the course of this time that the more I push it and feel uncomfortable, the worse it can get. We try to make small progressions."

He will likely taper down Friday after two days of activity, but that he adopted a rigorous routine for two straight days is a promising sign.

Utley said he was not at "full speed" doing his grounders, but he moved side to side and tested his knees with different routes.

"There's a little discomfort, but that's a part of the whole process," Utley said. "Last year when I started taking ground balls, it was a little uncomfortable as well, but the more I did it, the better I became at it."

Utley said his plan is still to play in games immediately once he travels to Florida. When that will happen is still unknown. He will not wait until he is pain-free because he may never get to that state.

"I wish I could tell you," Utley said. "Obviously the better I feel, the shorter it will take. But it's still going to take a little time to get to game speed, obviously."

Contact Matt Gelb at mgelb@phillynews.com or follow on Twitter @magelb.