Extremely unlikely. It is nearly impossible for a baseball player to have the same impact as a top NBA player, because of the differences in the logistics of the two sports. A great hitter generally only has 4-5 plate appearances per game, a great starting pitcher only pitches every five days, a great fielder would have an unusual game if he had five difficult chances.

The NBA greats can participate in almost every play of the game. The NBA has a reasonable progression of "impact" at each of its five positions, and lists such as the "50 Greatest Players" (which predates LeBron) are a reasonable measuring stick.

In MLB, one can argue that a true "game-changing" player will have been a first-ballot Hall of Famer, and one can even argue that the player should have received 90% of the votes on the first ballot. The players in MLB who have received 90% since 1970 are comparable to the subset of players in the NBA "50 Greatest" list who played in the last 40 years.

Outfielders: Rickey Henderson, Tony Gwynn, Reggie Jackson, Hank Aaron, Willie Mays
Corner Infielders: Wade Boggs, George Brett, Mike Schmidt
Middle Infielders: Ozzie Smith
Starting Pitchers: Nolan Ryan, Steve Carlton, Tom Seaver, Jim Palmer.

Not one catcher on the list. In fact, HOF catchers even voted in by the writers since 1970 are only Yogi Berra, Johnny Bench, Carlton Fisk, and Gary Carter.

So Harper's chances of being a "game-changing" catcher are rather slim. As a catcher, he will have more wear and play less games. His best bet is to move to right field, and try to become the Reggie Jackson of his era. But that will take more than baseball skills, it will take communication skills, especially in this era of WebGems and Twitter. Reggie Jackson wasn't just great, he had STYLE.

Finally, no players drafted first overall in the MLB draft is in the Hall of Fame, although Ken Griffey, Chipper Jones, and Alex Rodridguez are all likely candidates.

Although his ability and statistics are quite impressive, it's way too early to tell. Let's have him continue to perform at a high level for a few years, entering the pros and eventually the major leagues, if he makes it.

No... only because he will play every 4 to 5 games whereas LeBron plays every game.