It’ll be Nate Eaton in the leadoff spot for the Red Sox on Saturday afternoon. (Photo by Maddie Malhotra/Boston Red Sox/Getty Images) Getty Images By Chris Cotillo | ccotillo@MassLive.com WASHINGTON — As the Red Sox hope for a bounce-back start from struggling starter Walker Buehler on Saturday afternoon, they’ll do so with a brand-new leadoff man and a different-looking lineup against the Nationals. Third baseman Nate Eaton is leading off against lefty Garrett Parker, marking the first time all season he has done so. The right-handed hitting Eaton has made four starts for the Sox, all at third base. Boston has Romy Gonzalez at second base and hitting second; Marcelo Mayer isn’t in the lineup.