SAN FRANCISCO -- 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. His home run Monday off Nationals left-hander Gio Gonzalez not only was his second in four games, but at 464 feet, was the longest by a Giant this season.

In fact, the righty hitter's blast to right-center field was the longest to the opposite field in the majors this season, and the fourth-longest to any field.

"I just haven't seen many balls hit there, even in batting practice," gushed Giants manager Bruce Bochy of a shot that landed within a few feet of a plaque commemorating Barry Bonds' record-setting 756th home run in 2014.

"That's impressive," Bochy continued. "Just shows you how strong this guy is. That's an area where few guys can hit a ball."

Williamson also drove in a third run with a fielder's choice grounder, giving him five RBIs in his four games.

Before last week's call-up, the 27-year-old had 92 games of major league experience, including five at-bats against Roark.

As has been the case against most Giants in his career, Roark has dominated the head-to-head, holding Williamson hitless while striking him out three times.

Roark (1-1, 3.24) has faced the Giants seven times in his career, including four times as a starter. He's never lost, going 6-0 with a 2.02 ERA.

He's the only active pitcher with better than a 4-0 record against the Giants.

Roark was last seen in San Francisco contributing seven innings to a 3-0 shutout win for the Nationals last May. He allowed six hits and one walk, striking out six.

The 31-year-old has gone 3-0 with a 2.42 ERA in four games, including three starts, in San Francisco.

Attempting to win a second straight game to open a 10-game homestand, the Giants will counter with left-hander Ty Blach, who has pitched in hard luck this season.

Blach (1-3, 4.10) has received a total of eight runs of support in his five starts. He's coming off back-to-back losses of 5-1 at San Diego and 3-1 at Arizona.

He has never faced the Nationals in his career.

Blach will be facing a Washington team that's struggled to score runs without injured regulars Adam Eaton, Daniel Murphy and Anthony Rendon.

The Nationals, now 3-4 on a nine-game trip, totaled only eight runs while losing two of three in Los Angeles against the Dodgers, before managing only five hits and two runs against the Giants' Chris Stratton and three relievers on Monday.

Giants pitchers have allowed four or fewer runs in seven straight games.