SEATTLE -- It was a great Father's Day for Nationals outfielder/infielder Kory Casto.

With his father, Scott, and daughter, Kenzie, in the stands at Safeco Field, Casto had a big day. His pinch-hit homer in the top of the eighth inning helped the Nationals defeat the Mariners, 6-2, on Sunday afternoon. With the victory, the Nationals swept their first series of the season.

The score was tied at 2 when Washington rallied to take the lead off reliever Mark Lowe. The Nationals had runners on first and third when manager Manny Acta decided to have Casto pinch-hit for Wily Mo Pena, who has been in a season-long slump. Acta wanted someone who could put the ball in play.

"Kory was the best contact hitter we had there," Acta said. "He's not a strikeout guy. I wasn't thinking about him hitting a home run, but he does a good job of putting the barrel on the ball consistently, and with the infield in, anything could happen. I just thought the matchup was better."

Acta's hunch proved to be right. Casto launched Lowe's 0-1 pitch for a three-run homer, his first in the Major Leagues. The ball ended up hitting the right-field foul pole. Mariners right fielder Jeremy Reed protested that the ball was foul, but umpires got together and ruled it fair. The replays also showed that the ball hit the foul pole.

"With runners on first and third, I was trying to get something elevated in the outfield and score that run and stay out of the double play," Casto said. "I got a fastball elevated over the plate. I put a good swing on it. It barely hung on, but it hung on enough. It was the first one of my career."

The home run was even sweeter because he grew up in Salem, Ore., which is about three hours away from Seattle.

"I was a Kingdome Mariners fan," Casto said. "They didn't have Safeco Field when I was younger. I grew up watching Jay Buhner, Ken Griffey Jr. -- the good teams they had in the mid-90s."

After watching his son cross home plate, Scott Casto went toward the foul pole to retrieve the treasured ball. The father offered the fan who caught the ball $100, but the fan wanted two Nationals hats instead. They both went down near the clubhouse, and equipment manager Mike Wallace came through with the two hats for the fan.

Scott Casto already had Kory's last college home run when he was at the University of Portland. He wasn't going to allow his son's first Major League homer to get away. Kory Casto ended up with the ball, and the son gave the father his wristbands and a big hug. As he talked to reporters in the hallway, Scott's eyes welled and his voice was quivering.

"What a Father's Day. You can't beat that," Scott Casto said. "I'm absolutely wiped out right now. I'm watching the ball. I'm saying, 'Stay fair, stay fair.' Once it hit off the foul pole, it was quite a feeling. It was something really special. I don't even know how to explain it. I was really proud."

Casto wasn't the only one to do damage to the Mariners in the eighth inning. Three batters later, Elijah Dukes came home on a sacrifice fly by Lastings Milledge.

Jesus Colome was the winning pitcher, but starter Tim Redding was the pitching star for Washington, lasting six innings and giving up two runs -- one earned -- on five hits.

Redding was given a 1-0 lead in the first inning, when Jesus Flores grounded out to score Dukes.

Errors by second baseman Felipe Lopez and Dukes helped the Mariners tie the score in the third inning. The Mariners' Jose Lopez led off the inning with a ground ball to Felipe Lopez, who bobbled it and threw the ball into the Seattle dugout, allowing Jose Lopez to reach second base. Felipe Lopez was charged with two errors on the play.

After Jose Lopez reached third on a fly ball by Raul Ibanez, and Adrian Beltre's grounder marked the second out of the inning, Jose Vidro hit a routine fly ball to Dukes in right field. But Dukes dropped the ball, allowing Lopez to score.

Seattle then took the lead the next inning, when Ichiro Suzuki singled to right to score Willie Bloomquist.

"I think he did a very good job for us," Acta said of Redding. "We played shaky defense in that one inning. He really battled for us in that inning, and pretty much got himself out of it with men on third and less than two outs. He stayed in the game for six innings."

Redding ended up getting a no-decision after the Nationals scored the tying run in the top of the seventh. Flores had another RBI groundout.

Although he didn't get the win, Redding talked about how he happy he was for Casto to get the big hit on Father's Day.

"He is in his home region," Redding said. "He has family and friends here. It's his first Father's Day. He had a baby recently. I know his wife and kid are here. That's special."