Part 9 of a 10-part series that looks at prominent potential Hall of Famers for the Class of 2013 and the reasons to vote them in - or keep them out.

Sammy Sosa is in his first year on the ballot. The former Cub, who also spent time with the Rangers and Orioles, slugged his way into the baseball record books with 609 career home runs. But questions over how exactly he transformed from an average player into a great player may keep him out of the Hall of Fame.

THE CASE FOR THE HALL

Baseball has been very, very good to Sosa.

As Sosa prepares for his first shot at the Hall of Fame, he does so as the eighth-most prolific home run hitter in baseball history. He retired with 609 home runs -- more than Frank Robinson, Mark McGwire, Harmon Killebrew or Reggie Jackson. Every one ahead of him is either in the Hall of Fame (Hank Aaron, Babe Ruth, Willie Mays), still playing (Alex Rodriguez, Jim Thome), isn't eligible yet (Ken Griffey Jr.) or is eligible for the first time this season (Barry Bonds).

He finished in the top-15 of MVP voting every season from 1995-2003, winning the National League MVP in 1998 when he hit 66 home runs and led the league with 158 RBIs, 134 runs and 416 total bases. He finished second in 2001 after leading the league with 146 runs, 160 RBIs and 425 total bases. He led the league with 50 home runs in 2000 and led the league with 49 home runs and 122 runs in 2002.

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His 4,704 total bases are the 35th most in history.

His 1,667 RBIs rank 27th all-time.

His 1,033 extra-base hits are 27th best ever.

Every player ahead of him on each of those lists is either in the Hall, still playing, not yet eligible, is about to be on the ballot for the first time or has been banned from baseball.

Sosa became one of the faces of the game during the summer of 1998 when he and McGwire chased Roger Maris' single-season home run record. When McGwire became the first man to break the record -- during a game against Sosa's Cubs -- the two men embraced in a terrific and emotional moment for the sport.

From 1990-1998, Sosa hit double-digit home runs and stole double-digit bases all but one year, an injury-shortened 1992 (he still had 15 steals in 67 games that year).

After a year off from baseball in 2006, Sosa came back to hit .252 with 21 home runs in his final campaign with the Rangers at age 38.

When the Cubs lost a controversial NLCS in 2003, Sosa was not part of the problem. He hit .308 with two home runs in that series, making up for prior postseason failures.

Sosa's 93.1 combined career UZR (ultimate zone rating) is seventh-highest since 1900 for all primary rightfielders. UZR is an advanced stat that measures a player's ability to reach balls hit in his fielding zone. Aside from Hank Aaron's 98 UZR, no other player reached at least a 90 UZR who's hit at least 241 home runs.

THE CASE AGAINST THE HALL

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For many years, after the fun -- and the farce -- of the 1998 home run chase had ended, fans and writers looked back on that above-average player who became a one-dimensional, muscular slugger and wondered -- was it all real?

Then in 2009, the answer seemed to come: no.

Sosa allegedly was among 104 MLB players who tested positive for performance-enhancing drugs during a supposedly anonymous test in 2003, according to a New York Times report. The exact substance for which Sosa supposedly tested positive was never identified.

But that article gave credence to what the "eye test" had told spectators for many years: Sosa was a juicer. Heck, throw out the eye test. Just check the numbers.

From 1989-1997, Sosa hit 40 homers once. During those first nine years of his career, he hit 207 home runs, batted .257, had a .308 on-base percentage, a .469 slugging percentage and a .777 OPS. He was selected to one All-Star game, won one Silver Slugger and had three top-20 MVP finishes, only reaching as high as No. 8. Still a speedy player, he stole 199 bases.

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From 1998-2007, Sosa hit more than 40 home runs five times and more than 60 home runs three times. During those final nine seasons of his career, he hit 402 home runs, batted .287, had a .372 OBP, a .588 SLG and a .960 OPS. He was elected to six All-Star games, won five Silver Sluggers and had six top-10 MVP finishes, including one win. Now a cumbersome, slow player, he stole only 35 bases.

The argument can be made for some of the other suspected steroid cheats - Roger Clemens and Barry Bonds, in particular -- that they were Hall of Famers before they ever allegedly injected anything.

The same cannot be said for Sosa.