BALTIMORE -- Just when it appeared as if the Baltimore Orioles had righted themselves, bad news arrived in the form of an unfavorable medical report.Soon after the Orioles beat the Washington Nationals 8-1 on Tuesday night, manager Buck Showalter confirmed that ace Chris Tillman is likely to be sidelined with a sore right shoulder.I think hes going to be on the disabled list, Showalter said. They were talking about whether or not they were going to inject him. ... I think that would be a sign of where he is heading.Tillman is 15-5. No other starter on the team has more than seven wins.Were trying to be safe, get this thing in the rear-view mirror, Tillman said. That way Im not fighting it all year.If the Orioles are to stay in contention for the AL East title or a wild-card berth, theyre going to need more pitching performances like the one they got from Kevin Gausman, who scattered six hits over six shutout innings.Adam Jones went 4 for 5 and Chris Davis hit his 30th home run for the Orioles, who won two straight over Washington to conclude a 3-5 homestand.Theyre one of the best teams in baseball and in that league, so it was tough, Showalter said.Baltimore is 34-24 against the Nationals in a rivalry that began in 2006. The series shifts 38 miles south to Nationals Park on Wednesday for the first of two games.Gausman (5-10) walked two, struck out two and permitted only one runner past second base. Hes 5-1 at home and 0-9 on the road.Ive pitched well on the road. I just dont necessarily have the wins to show for it, the right-hander said.The 25-year-old Gausman outpitched Nationals rookie Reynaldo Lopez, a 22-year-old making his fifth major league start. Lopez (2-2) yielded six runs, four earned, and seven hits in 2 2/3 rocky innings.The results were not what I expected, Lopez said through an interpreter. The game did not go the way I liked it to.Trea Turner had a career-high four hits for Washington. The Nationals trailed 6-0 after three innings and went quietly in their third straight loss -- their longest skid since a seven-game run from June 18-25.Its good to be going home. It seems like we havent been home in a while, Baker said following the conclusion of a nine-game road trip. We go home and regroup. Guys get to see their kids and their wives.Replay did the Nationals no favors. Turner was called safe on steal attempts in the first and thir