OAKLAND, Calif. — Jonathan Villar is to play multiple positions at Class AAA Fresno — second base, shortstop, third, left field and center — so that he can continue his growth as a super utility player. Villar was optioned to the minors ahead of Friday’s game to make room for reliever Josh Fields’ return from the disabled list, pushing the Astros to 13 pitchers, one more than they opened the year with.