Washington Nationals right-hander Tanner Roark will put an impressive streak on the line Tuesday when he faces hot-hitting Mac Williamson and the San Francisco Giants on the second night of a three-game series. The Giants won the series opener 4-2 on Monday, getting a two-run homer and three RBIs in all from Williamson, who was promoted from the minors just last week when Hunter Pence was placed on the disabled list. Williamson has wasted no time making an impression on the Giants.