Oakland Athletics relief pitcher Sean Doolittle is expected to begin a rehab assignment this weekend as he recovers from a left shoulder strain, according to the San Francisco Chronicle. Doolittle completed a simulated game Tuesday, which reportedly went well, and barring any setbacks will be cleared for a minor league assignment. He has been limited to only one appearance this season due to separate shoulder strains. Upon his return, he could push Edward Mujica for ninth inning responsibilities. Mujica just inherited the closer job following the trade of Tyler Clippard last week. Doolittle saved 22 games last year for the A's in 61 appearances, posting a 2.73 ERA and 0.73 WHIP over 62.2 innings while striking out 89. Doolittle struck out 60 in each of his first two seasons as a set-up man, posting an ERA of 3.13 or lower and a WHIP of 1.08 or lower.