ST. PETERSBURG, Fla. -- Hideki Okajima was unavailable for Monday night’s 6-5 loss to the Tampa Bay Rays because of a stiff back, Red Sox manager Terry Francona said, a condition that has bothered him at least off and on for a couple of weeks. Okajima last pitched June 29 against the Rays in Boston.

Okajima’s back problems are likely to accelerate Boston’s search for left-handed relief help heading toward the July 31 trading deadline. Okajima has hardly been the reliable out producer he was in the past -- he is 2-2 with a 5.81 ERA, and opposing hitters are batting .324 (36-for-111) against him, with lefties hitting him at a .308 (16-for-52) clip.

Here are some names of left-handed relievers to keep an eye on:

* Scott Downs, Toronto.

* Will Ohman, Baltimore.

* Sean Marshall, Chicago Cubs.

* Javier Lopez, Pittsburgh

* Craig Breslow, Oakland

Of the lefties on the market, Downs and Ohman will be at the top of most teams’ lists. Lopez and Breslow have both been with the Sox before, while Marshall, according to one major league scout, doesn’t have the stuff to compare to Downs and Ohman, but is a veteran with a decent track record.