With 17 home runs in the 101 games he has played this season, Alex Rodriguez is on pace to hit just 27 for the year. That puts him on target to catch Sammy Sosa (609) in late September. Ken Griffey Jr. (630) is likely during the 2011 season and Willie Mays (660) in 2012.
After that, if A-Rod does not go on a HR tear, it gets more difficult. Fifty four homers separates Mays from Babe Ruth (714), so that could take the better part of two seasons. Perhaps by 2014, when Rodriguez will turn 40.
Then, Hank Aaron (755) and, finally, Barry Bonds (762) will be in sight. And A-Rod will have to deal with all those questions about the legitimacy of the record.
All of this assumes he remains healthy.