After two years in which Sizemore didn't play a single game in the Major Leagues, it was unfair to expect he could pass all the tests that would come his way in Spring Training.
Yet so far, that's exactly what Sizemore has done. He took another significant step Tuesday, starting back-to-back games for the first time in Spring Training.
With each passing day, Sizemore feels like more of a baseball player again, one who could develop into one of the best comeback stories of the 2014 season.
"I wasn't all that curious about it," Sizemore said of playing back-to-back. "I felt confident knowing it was going to be a pretty normal day. If I had any questions or doubts, I probably wouldn't have been out there. But I felt strong that it was going to be fine and it wasn't going to be an issue."
In Sizemore's first at-bat, he hit a grounder that deflected off the glove of the second baseman, creating a chance for an infield hit. Sizemore was thrown out by about a step, but he continues to make good time down the line.
Sizemore, who went 0-for-2 on Tuesday, has played in five Grapefruit League games, batting .308. He looks mobile in the outfield and has impressed the Red Sox with his swing.
The things that Sizemore is trying to find now are all things he should regain simply with time.
"I feel good, but not great. My timing feels off," Sizemore said. "It feels a little rusty, but I don't feel like it's been two or three years. I feel like it's just another Spring Training where it's early where you're just trying to get a hold of things and get that rhythm down. I still feel like I have a long way to go. It's not quite where I would like it to be and I want to fine-tune some things."
In giving Sizemore a one-year, $750,000 contract -- with incentives that could bring the deal up to $6 million -- the Red Sox made a deal that made sense for everyone.
And with less than three weeks to go in Spring Training, there are signs that it could, in fact, be the win-win both sides were hoping for.
"Grady, he looks pretty darn good for me," said right fielder Shane Victorino.
Though it's easy to forget that Sizemore was an elite player not all that long ago, his new teammates remember it well.
"As I told him before, 'Four or five years ago, I looked up to you as a center fielder, to want to do what you did in center field.' It's obviously there," said Victorino. "It's just a matter of him physically feeling good about his body and going out there every day and doing it.
"As I said, I don't think those things leave you. If we can get Grady healthy, and obviously he looks good out there, I think we all know what he can be. And I'm excited and hopefully he can stay physically strong and be out there and play alongside of him."
The competition for Sizemore is Jackie Bradley Jr., a highly-regarded prospect who is already a plus defender and projects to be a productive hitter in the Majors.
But with young players, you never quite know when it will click.
With Sizemore, it's fairly safe to assume that if he is healthy, he will produce.
It has been a long road back to this point for a player who had microfracture surgery on both knees and also some back and left elbow issues.
After coming through all that, Sizemore is younger than you would probably guess -- at 31 years old.
Manager John Farrell, who was Sizemore's farm director throughout much of their time together in Cleveland, is encouraged by what he sees on a daily basis.
"Not far off," Farrell said of the Sizemore he saw then vs. the one he sees now. "But yet you temper that past impression because of what he's endured and the physical challenges that he's had to overcome. What has stood out this spring is his timing at the plate. You would think it would have needed a greater number of at-bats to have the timing that he's showing right now. That's extremely encouraging."
The Red Sox wouldn't have wasted their time on signing Sizemore if they didn't think he had at least a decent chance to succeed.
"Through our medical exam prior to signing him, we felt like he was a good bet and had every opportunity to get back on the field and maintain that," Farrell said. "To what level of games played, we don't know that."
The answers will come in time.
"It was good," said Sizemore. "Everything went well. Another good day."
At this point, that's about all Sizemore can ask for.