Nats hold 2-0 lead over Houston (make that 4-0)

VIERA, Fla. - The buzz inside Space Coast Stadium just prior to first pitch was all about Bryce Harper being scratched from today's game because of left calf tightness. Edwin Jackson gave everyone something else to talk about. Jackson threw four scoreless innings against the Astros this afternoon, allowing just two hits and striking out three. The righty showed off impressive offspeed stuff today, and looked really sharp early, setting down the first six batters he faced. Ross Detwiler will replace Jackson to start the fifth inning. The Nationals hold a 2-0 lead over the Astros through four frames, with Ryan Zimmerman's solo home run and Eury Perez's bloop single providing the Washington runs. Zimmerman's first-inning shot went to the opposite field. The longball was definitely aided by a stiff wind blowing out to right, but hey, it counts. It's the first homer of spring for the new $100 million man. In Zimmerman's second at-bat of the game, he ripped a shot right back up the middle that nailed Astros pitcher Livan Hernandez on the leg. Hernandez tracked down the ball and threw Zimmerman out at first, but subsequently left the field with a trainer. Perez's bloop to center drove in Brett Carroll, who doubled with two outs in the second inning. Update: The Nats tacked on two more runs in the fifth on RBI singles by Zimmerman and Jason Michaels and now lead 4-0. Zimmerman's knock scored Anthony Rendon, who pinch-ran for Steve Lombardozzi after Lombardozzi led off the inning with a double to right. Three batters after Zimmerman's RBI single, Michaels slapped a single to right, scoring Mark Teahen, who pinch-ran for Zimmerman. Detwiler has thrown two perfect innings for the Nats, striking out two. Dan Kolko was named MASNsports.com's Nationals beat writer after spending the last four years covering the Baltimore Ravens for MASN and also serving as the Web site's deputy managing editor. A University of Delaware graduate originally from Silver Spring, Md., Dan grew up a die-hard baseball fan and is thrilled for the opportunity to cover the Nationals. Before joining MASN, Dan worked in production at Comcast SportsNet in Bethesda, Md., and also interned at the "George Michael Sports Machine" in Washington, D.C. Follow Dan Kolko on Twitter: @DanKolko