What's next for Lopez and Giolito?

Reynaldo Lopez revealed both weaknesses (a very hittable fastball) and strengths (a very unhittable curveball and changeup) in his major league debut last night, enough to leave the Nationals plenty intrigued to see more of the 22-year-old.

"He's young, this is the big leagues, and you're facing big-league hitters," manager Dusty Baker said after Lopez gave up six runs and 10 hits but struck out nine in 4 2/3 innings. "But he's very bright. Just gotta tighten up a few things. I think he'll be here for a long time."

But will he still be here the next time his turn in the rotation comes up? That remains to be seen.

The Nationals next need a fifth starter Sunday against the Padres. Lopez is lined up to make that start, but so is fellow prospect Lucas Giolito (who started for Triple-A Syracuse last night).

Meanwhile, Joe Ross is being positioned to make his return from a minor shoulder injury on the same schedule. Ross (out since July 3 with right shoulder inflammation) still needs to make at least one, probably two, minor league rehab starts, but before long he'll be ready to return and reclaim the spot he vacated.

What do the Nationals do in the meantime? Lopez certainly offered up enough positives last night to warrant another look. But Giolito is the more highly touted prospect and tossed 6 2/3 strong innings last night against Gwinnett, allowing just one unearned run.

"It's no coincidence that Giolito and Ross and Lopez are all scheduled on the same type of rotation," general manager Mike Rizzo said earlier in the day.

The Nationals figure to see more of both young right-handers over the rest of the season. And if everyone else in the rotation is healthy, that could come out of the bullpen.

"We're going to put our best 25 on the field at any given time," Rizzo said. "We're certainly not there yet. We're not looking that far ahead of ourselves. We need to win tonight and we need to play good baseball throughout. We've got a tough division of teams that's playing well. We're focused on that right now."

When the time does come, the Nationals want to have as much firsthand knowledge of both pitchers to make a well-reasoned decision. They got a taste of Lopez last night, getting a better sense of what he might bring to the table later on.

"Yeah, that helps me have a vote, and have a genuine vote," Baker said. "If we get in a room and we say, 'Who do we think can be a September call-up,' am I voting on numbers or what somebody else told me? Or am I voting possibly on what I see? I'd rather vote on what I see, you know, even if it's just a glimpse of that person."