Stall in Mac's chase is painfully evident.(The Dallas Morning News)

DALLAS _ The marvelous thing about Mark McGwire is that he has hit 67 home runs in his last 162 games.

The depressing thing about Mark McGwire is that you have to count back to July 23, 1999, to cover the last 162 games he has played.

Big Mac made an appropriately loud return this week, slamming a home run Monday against Milwaukee in his first game since spending another six weeks on the disabled list trying to rehabilitate his damaged right knee. But rather than a cause for celebration, career home run No. 556 only served to remind us what we've been missing. McGwire's knee limited him to only three games and seven at-bats all week.

Blessed with the good health, keen eye and extraordinary power to crush a record 70 home runs in 1998, McGwire has since been betrayed by his body. Since breaking Roger Maris' single-season record with his 62nd home run on Sept. 8, 1998, McGwire has been limited to 270 games (and 107 homers in 843 at-bats) over the last 2{ seasons.

The knee that required off-season surgery last winter to remove portions of a diseased patella tendon is responsible for nearly four months spent on the disabled list, and for a frustrating September 2000 when McGwire was allowed only one at-bat per game for the playoff-bound Cardinals. All told, McGwire's long history of back, heel and knee troubles have led to eight stays on the disabled list at a cost of at least 350 games in the prime of his career. He has St. Louis team trainers feeling more jittery than Jenna Bush's Secret Service detail.

That McGwire has become the greatest slugger in the game's history is open to little debate. Reduced to their simplest elements, the numbers show McGwire has averaged in his 15-year career one home run for every 10.64 at-bats, and 50.4 homers for every 162 games played. Babe Ruth averaged one homer every 11.76 at-bats and 46.2 homers for every 162 games played. And career home run king Henry Aaron homered once every 16.38 at-bats, and just 37.1 times for every 162 games.

But Aaron's career record of 755 home runs looms ahead of McGwire like a mirage. Currently seventh on the all-time list (just seven behind Reggie Jackson), McGwire trails Aaron by 199 homers, a margin that could be made up in about four seasons if McGwire was younger and healthier. Given the delicate condition of his knee, and the fact he turns 38 on ...