Now a TBS analyst and agent, Sheffield believes Baez needs to make a mechanical adjustment to improve his at-bats, while the Cubs are mostly concerned with his approach at this point.
Sheffield said he watched tape of Baez in the Cubs' hotel suite during the winter meetings in December 2013 and has been watching him since he was called up from the minors in August.
"When I saw this guy swing [in December], I knew he was going to be a big leaguer for them soon," Sheffield told ESPNChicago.com on Tuesday. "Right now when I watch his swing, he has something in his swing that can be fixed real easy. He collapses his back leg. And anytime you do that, a pitcher is going to have a field day on you.
"When you collapse your back leg, anything over the belt line you have to uppercut. You can't stay on top of it."
The 21-year-old Baez, who was the Cubs' top draft pick in 2011 and was ranked as the eighth-best prospect in baseball by ESPN.com Insider Keith Law, made an immediate impact when he was called up, hitting three home runs in his first three games.
While Baez has shown glimpses of the tremendous power he flashed in hitting 60 home runs in his last two minor league seasons, his two-month stint with the Cubs has been plagued by strikeouts. He has fanned 88 times in 195 at-bats along with nine homers.
The Cubs say they aren't concerned with how the outs are made, so much as how many are made. For now, Baez is being allowed to be himself at the plate, and mechanical changes -- if needed -- will come later.
"Keeping that back foot anchored is important," Cubs hitting coach Bill Mueller said. "It's necessary for sure in keeping square. What's most important is him getting games played. It's a small sample size."
Manager Rick Renteria added: "When we look at his film, the one thing that stands out is if he swings at strikes, he does damage. When he swings at balls, he doesn't. That has nothing to do with mechanics."
Sheffield disagrees, to an extent.
"I see all the ability," said Sheffield, who hit 509 home runs in 22 seasons. "And I see someone has to get with him real quick and fix that little mechanical issue that he has before it gets worse. When you're trying to create that much torque with your lower half collapsing, that's a lot of moving parts. People would ask me, 'How could you do that with all that wiggling the bat like that?' Because it's not how you start it's how you finish. I was always focused on my finish, not how I start."
Sheffield sees the similarities between himself and Baez as everyone else does, but he still can't comprehend the strikeout totals. Sheffield actually walked way more than he struck out (1,475 bases on balls to 1,171 strikeouts) and never struck out more than 83 times in a season. But he was a throwback, in that respect, and one of the most feared hitters of his time. His career on-base percentage was .393.
"How is taking walks going to make my numbers improve when I'm not getting the opportunity to swing the bat?" Sheffield asked rhetorically. "That 1-for-3 day with a walk adds up over time as opposed to being 1-for-4. When you put those numbers together, with runs scored and driven in and all those things, it's a prettier stat."
Baez and fellow rookie teammate Arismendy Alcantara, 22, have terrible walk-to-strikeout ratios, but that's not unusual for their age and experience. Obviously, except for the rare few, a couple of months in the major leagues usually doesn't produce good numbers for very young players. The experience is what counts.
"The key is not making outs," Cubs president Theo Epstein said recently. "I don't care about the strikeouts if you have a good approach and you're squaring up the balls you should."
Baez's approach is part of bigger concerns for Renteria right now. Baez has been susceptible to the high fastball and the breaking ball away; he wouldn't be the first. But there is progress. After striking out in his first two at-bats Tuesday night against the St. Louis Cardinals, Baez worked the count full before laying off a high fastball and drawing a walk in his third at-bat.
Sheffield is mystified that players today don't know how to situational hit and then go down swinging way too much.
"As a baseball player, you have the responsibility for what you do in that batter's box," he said. "If you're striking out that much, and he just got called up, that's almost like you don't even have a clue that you're going to make contact when you get up. That, to me, is a sign of disaster. It may look good that he has bat speed and all that, but once people find out they can strike you out easy, then it's going to get worse for you than better."
Of course, Baez is not alone in his propensity to strike out. Teams are averaging 7.7 strikeouts a game this season, the highest in history, according to baseballreference.com, and that figure has been trending up for the past nine seasons.
Sheffield started his career at a time when strikeouts weren't as prevalent and even accepted as they are now. In 1990, when Sheffield broke in with the Brewers at age 19, there were 37 players in baseball who struck out at least 100 times, according to baseballreference.com. This season, that total is 107 with five days left in the regular season, and 17 more players are within five strikeouts of 100.
"Fundamentals were drilled into our heads, and we were pretty much embarrassed to strike out," Sheffield said. "When I played pro ball and I struck out, I was probably the most embarrassed on the field. Kids nowadays, they don't have to work as hard as we did to get to where they're at. They take certain things for granted, and they don't care about certain things. And striking out is one of them."
Sheffield views his comments on Baez more as a warning than a criticism. He has wanted Baez to succeed ever since the Cubs showed Sheffield video of their elite prospect in December.
For now, Baez says he's just trying to hit the ball, and he'll worry about the rest after the season. That's in line with what the Cubs want, as well. One thing at a time.