But just how much more clout will advice from Big Mac carry than a hitting coach with a less-accomplished resume, or even one that has never played in the Major Leagues? It's an issue Minnesota Twins hitting coach Joe Vavra knows too well.
"Once I got the position and there were some questions raised about my credentials, I don't know if I was prepared for that," Vavra said. "I just thought I was going to get the job, kind of quietly get the job and just go to work. Get the guys working, work with the team. I don't know if I was quite prepared for some of the controversy that came."
Vavra became the Twins' hitting coach prior to the 2006 season when he was promoted from Minor League field coordinator. Given that Vavra had never played in the Major Leagues and with Paul Molitor having turned the job down, some players, including All-Star outfielder Torii Hunter, publicly expressed their concern.
Vavra, who is entering his fifth season as hitting coach, has since helped Joe Mauer win three American League batting titles and Mauer and Justin Morneau earn AL Most Valuable Player awards.
"I oversaw the development and operations, so it was going to be a relatively easy transition in terms of the job, because, basically, I had watched many of them come up," Vavra said. "They were comfortable working with me, and I was comfortable working with them. They had not worked one-on-one with me in hitting sessions, but I knew that we would be able to build a good work ethic together.
"What I was trying to get across to the players was that you work and train the body, and that will solidify the mind. ... Success is all about confidence."
There are only seven hitting coaches among the 30 Major League teams who never played in the Major Leagues: Kevin Long (Yankees), Jim Skaalen (Oakland), Rick Eckstein (Washington), Rudy Jaramillo (Cubs), Don Long (Pittsburgh), Derek Shelton (Tampa Bay) and Vavra.
Others, such as McGwire, Kevin Seitzer (Kansas City), Terry Pendleton (Atlanta) and Don Mattingly (Los Angeles Dodger), were accomplished hitters.
Jaramillo, who previously worked with the Houston Astros (1990-1993) and Texas Rangers (1995-2009), is one of the most respected hitting coaches in the game, despite having never played above Class A. While in Houston, he helped turn a then-unknown Jeff Bagwell into the 1991 National League Rookie of the Year.
"I think Rudy got me to the point where he made me think better of myself and what I thought I could do," Bagwell said. "I just think he has a total understanding about what to do and how to go about getting people to hit better. He's a tireless worker, too, which helped."
Jaramillo signed on to be the Cubs' hitting coach this year, and the fact he has no Major League experience as a player doesn't bother Chicago catcher Koyie Hill.
"Rudy's a teacher," Hill said. "He's the guy who doesn't tell you what you're doing wrong. He says, 'How can we fix it for you?' It's not the same for the next guy or the next guy. It's simple. It's like a teacher in school. They'll teach you what you need to know in order to succeed. I think Rudy is going to help us big time."
Vavra's situation is proof players can be won over by a hitting coach, as long as there is strong communication and the teaching skills are solid. Seitzer, a career .295 hitter in 12 Major League seasons, believes players discover quickly if a hitting coach has the right stuff.
"Players aren't stupid, and they can say, 'This guy's got it going on; this is good stuff. He's going to help me; he knows what he's talking about,'" Seitzer said. "But if they say, 'He's just a big-name guy, he's trying to make me what he was and do the things he did,' that doesn't work for me.
"Players will be very respectful [and] open and listen, but you can tell if they're really soaking it up or if they're just being respectful. Everything I've heard about McGwire, as far as a hitting coach goes, are great things. If he gets the results -- and that's the bottom line -- it'll be fun for him."
Rangers slugger Josh Hamilton, who blossomed under Jaramillo in Texas, doesn't think playing experience translates into being a good hitting coach.
"If the guy has been around the game a long time, no matter what his numbers were, [he's] been around enough to know what [he] doing," Hamilton said. "If they don't know what they're doing, they wouldn't be around."
The jury is still out on McGwire, who has yet to spend one day on the job. He hit 583 homers in 16 seasons and was one of the most feared sluggers of his generation, but his recent admission that he used steroids at different times during his playing career to help recover from injury has tainted his legacy.
Still, players like Matt Holliday and Pujols believe McGwire brings a lot to the table.
"I called Hal [McRae] when they decided to hire Mark, just to let him know how much I appreciated the work, to have him as a hitting coach for five years," Pujols said. "It was a great experience, and I'm pretty sure I'm going to learn a lot from Mark, because he has probably different things as a hitter.
"If he says something that I don't agree [with], I don't use it. I go out there and take my own plan. But I'm open to hear from my teammates. I'm open to hear from my hitting coach, from my manager, from my coaches. That's how you get better in this game."
Pujols said McRae challenged him and used positive reinforcement, even on days the slugger thought the bat weighed 100 pounds. Those are the kinds of things hitting coaches need to do, he says, no matter their background.
"It's more than just letting you know that you're dropping your hands or you're jumping at the ball," Pujols said. "It's different things. That's a relationship that you build with a hitting coach. Hopefully, it works for me and Mark.
"I don't think I'm going to have any problems getting along with him, because he was with our ballclub in 2001, and I saw the work ethic. I'm a big believer in using the tee, and he's a big believer in using the tee, so that's a plus."
As Vavra can attest, being a successful hitting coach is a challenge that encompasses many things, from relationships with players to work ethic and teaching methods. But he's proof that strong credentials as a Major League player aren't a job prerequisite.
"It's not about what you did or what your background is, it's all about what can you do for the player," Vavra said. "That's the way I went about it. The whole philosophy I go by is that it doesn't matter who gets the credit, as long as you get the job done.
"You can accomplish great things if you don't worry about who gets the credit. I believe in that. It's all about getting the player to do what he can do -- the best that he can do it, to his abilities -- and get the most out of him. That's the part that's enjoyable as a hitting coach.
"I know that there is a lot of negativity in hitting and a lot of outs made and a lot of Oh-fors on tough nights. As a hitting coach you are going to have to wear that a lot, and I do. When we have a good night, I'll still go home thinking about the guys that didn't hit and how can I get them going. I don't know if I'm ever satisfied or happy. I'm happy when we win."