WASHINGTON -- The Nationals appear ready for the postseason. Smacking three home runs, the Nationals took down the Phillies, 5-1, to clinch the No. 1 seed in the National League playoffs. Ryan Zimmerman, Tyler Moore and Michael Morse went deep to support Edwin Jackson (10-11), who allowed one run in 6 2/3 innings. The Nationals won a franchise-best 98 wins this season and earned home-field advantage throughout the postseason. They finished at a regular-season best 98-64, the best record in the majors, barring the Cincinnati Reds result against the St. Louis Cardinals later Wednesday, and will play Game 1 of the NL division series Sunday at St. Louis or Atlanta. The Phillies finished the season a disappointing 81-81, ending a run of nine straight seasons with a winning record. Philadelphia scored first in the fourth inning when Carlos Ruiz doubled and eventually came home on a sacrifice fly by Darin Ruf. The Nationals answered in the bottom of the frame. Ryan Zimmerman led off with his 25th homer of the season, taking a Cliff Lee (6-9) fastball out to right field. Michael Morse and Tyler Moore followed with back-to-back doubles for a 2-1 Nationals lead. Moore added his 10th homer of the season, a mammoth shot to left to lead off the sixth. Facing Phillies' closer Jonathan Papelbon in the eighth, Morse slammed a two-run shot, his 18th of season, that gave the Nationals a 5-1 advantage. Jackson six hits and struck out six in his 31st start of the season. The right-hander became the fifth Nationals' starter with at least 10 wins this season. NOTES. Manager Davey Johnson said Stephen Strasburg won't be on the postseason roster. ... The Nationals will have some position players at their training facility in Florida and three or four pitchers working out in D.C. during the postseason in case they are needed. ... Nationals' left-hander John Lannan still is under consideration because of his success against the Atlanta Braves in his career. He is 9-5 overall and 5-3 at Turner Field. ... The Phillies and Nationals split the season series, 9-9. ... Phillies shortstop Jimmy Rollins sat out the Nationals series with a sore calf.