SCOTTSDALE — With less than two weeks until Opening Day, the Giants are still trying to figure out which pitchers will emerge as their best relievers. One potential option is headed for tests on his elbow, potentially knocking him out of that race. Right-hander Hayden Birdsong felt soreness in his right elbow during an outing on Tuesday and will get checked by team doctors, manager Tony Vitello confirmed after Thursday’s spring training game. The news first was reported by the San Francisco Chronicle. Birdsong has had an up-and-down spring but showed promise on Tuesday, striking out one in a scoreless inning and hitting 99 mph. Vitello said he caught up with the young pitcher before Thursday’s game.“(He’d) like to know what’s going on, so they’re looking into that,” Vitello said. “Obviously on a personal level you want what’s best for each one of these guys … he’s one that everyone has gotten close to because of his likability, coachability and his talent, but as of right now it’s out of my hands. I’m not a (medical) expert.”The Giants likely will be...