FORT LAUDERDALE, Fla. -- Scratch off two nagging question marks for the Orioles. Baltimore saw Jeremy Guthrie return from the World Baseball Classic on Monday and Koji Uehara complete a comeback from a strained left hamstring on Tuesday, confirming that all is well for the two sure things in the starting rotation.

After weeks of hand wringing over the uncertain elements of their starting staff, the Orioles have a better feel for the things they can count on come Opening Day. Uehara showed no lingering effects from his ailment and struck out seven Washington batters in an uncharacteristically overpowering outing.

"Obviously, we need him. That was big for us. That was big for everybody in this whole room," said pitching coach Rick Kranitz. "As it stands, we've got other candidates, but there's really two guys that are there. We haven't made any decisions on anybody yet, and obviously there are some guys that aren't in the mix anymore. But yeah, that was huge. We're counting on him. We're counting on him to be out there every fifth day."

Aside from a leadoff triple by Roger Bernadina, Uehara was fairly dominant. The 10-year veteran of Japan's Central League threw 40 of his 57 pitches for strikes and didn't walk a batter in his return. The Orioles hope he can get two more Spring Training starts before making his Major League debut against the Yankees in the second game of the season.

Uehara, who often speaks in cryptic sound bites translated by interpreter Jiwon Bang, said that the performance was a necessary first step in proving that he's healthy for the Opening Day rotation. But when he was asked if he's fully over his injury, Uehara took a refreshingly honest approach and said that he's not sure yet.

"I'm glad nothing happened -- in a good way," Uehara said through Bang. "I didn't have to cover first base, which was good. In terms of the fear [of aggravating the injury] going away completely, I don't know."

Uehara, who had strained his hamstring on March 9 against the Mets, had been working out gingerly on his own over the past two weeks. The right-hander only recently returned to jogging, and he faced hitters for the first time since the injury on Sunday. And in that same day, he learned a pitch that might change his season.

In the moments before taking the mound for his bullpen session, Uehara learned the grip for a circle changeup. He took it to the mound with him Sunday and used it again Tuesday to three different hitters. And while the pitch is still a novelty at this point, the Orioles feel it can alter his arsenal against left-handed hitters.

"I think the changeup will keep people honest," said manager Dave Trembley. "It's just another weapon for him. He likes it and his arm speed is great. ... He threw some curveballs today, and I think it was the first time all year his curveball was effective, too. There's such a difference between the speed of his curveball and his fastball."

And now, his changeup acts as the same kind of offering, reducing the strain on his split-fingered fastball. Kranitz said that some pitchers take months or years to really learn a changeup, and that Uehara is extremely rare in his ability to seamlessly learn the pitch and then bring it out to the mound with him.

More to the point, Kranitz said that it doesn't matter how big the separation in velocity is between the changeup and the fastball. As long as it gets hitters out on their front foot, it's worth the risk in throwing it.

"If the changeup's good enough and the arm speed's good, it doesn't matter," Kranitz said of the actual difference in speed. "It could be a four mile per hour difference as long as the hitter gets off the fastball."

Uehara said that he finds it more productive to test pitches against hitters instead of in the bullpen, and he also said that he could see the changeup becoming an important part of his repertoire. Whether or not that becomes the case, Trembley said that the game was reassuring if also validation for a pervasive gut feeling.

"You had to like what Koji did today. The first time he's thrown a changeup and he did a real nice job of that," Tremebley said. "It's great to have him back. I had no doubts that he would just pick up where he left off. He did that."