What about Adrian Beltre?

(Warning: The trade talk ahead is all contingent on the Red Sox deciding David Ortiz isn't going to play a key role in their lineup this season. That's not a step they've so far been willing to take; if Ortiz can't build on his pandemonium-inducing home run on Wednesday, though, they might not have that choice.)

Speculation so far has centered around the Red Sox adding a slugger who can play first base but who primarily would be penciled in as the team's designated hitter. If the Red Sox can get someone like that -- a Victor Martinez, perhaps -- they might be satisfied. But if they can't get someone like that, they might be better served looking at an upgrade on the defensive side.

Here's a theory: If David Ortiz isn't an everyday player, could the Red Sox be a better team with the aging Mike Lowell as its designated hitter and a stronger defensive player at third base?

Lowell has been an above-average defensive player ever since he was traded to the Red Sox. His Fielding Bible plus-minus (for plays made as compared to what an average player at his position would make) was plus-6 in 2006, plus-7 in 2007 and plus-7 in 2008.

So far this season, though, he's at minus-12. His "Ultimate Zone Rating" is at minus-2.0, meaning he's cost the Red Sox two runs. (Washington's Ryan Zimmerman leads all third basemen with a plus-6.7, meaning he's saved the Nationals 6.7 runs.)

Lowell still is a capable hitter post-hip surgery, but he's part of the problem on the left side of the Red Sox infield. Should the Mariners fall out of contention, though, Adrian Beltre might be the type of player who could fit nicely at third base for the Red Sox.

A year ago, Beltre finished the year with a plus-32 in the Fielding Bible ratings. So far this year, he's fourth among big-league third basemen with a 4.1 UZR. He's had some error issues, but his range is statistically better than any third baseman in baseball other than Zimmerman.

Oh, and he can hit a little bit, too. He's hitting just .213 this season and hasn't walked nearly as much as he used to walk, but his BAPIP is low (.248) and he's someone who normally is good for 20 home runs a year with a .450 slugging percentage. (He has two home runs so far this year.)

Beltre's five-year, $64 million deal with the Mariners expires after this season. He's been a fixture in trade rumors for the past year -- he would have been a great fit for the Twins last summer, but nothing ever happened. His name hasn't been tossed around much this year because the Mariners are hanging around in a fairly weak American League West.

But if the Mariners start to slip -- they were five games back entering play today and have allowed more runs than they've scored so far this season -- Beltre might land on the block.

Can you envision a Beltre-Jed Lowrie left side of the infield?

Doesn't that sound appealing?