Krook elected to enter free agency Wednesday after declining his outright assignment from the Nationals to Triple-A Rochester.
Krook was DFA'd by the Nationals on Monday, and rather than remain in the organization, the veteran southpaw will have the opportunity to explore his options. He's appeared in 11 major-league games between the Nationals and Athletics this season, allowing 11 runs (10 earned) on nine hits and 10 walks while striking out nine across 9.1 innings.