Giolito, Lopez set to join Potomac

A pair of highly ranked Nationals prospects will make their season debuts this week.

No. 1 Washington farmhand Lucas Giolito and No. 4 Reynaldo Lopez were assigned to Class A Advanced Potomac on Tuesday after starting the year at the team's extended spring training camp in Viera, Florida.

Lopez will start Wednesday against Wilmington while Giolito, considered the the top pitching prospect in baseball by MLB.com, will take the bump two days later against Frederick.

Assistant general manager Doug Harris told MLB.com there was nothing wrong with either pitcher and they were kept back for the first month of the season to "build volume" and increase their arm strength.

"We started their throwing program when they came to us. So they were a few weeks behind," Harris told MLB.com.

Giolito, selected by the Nationals 16th overall in the 2012 Draft, has rarely struggled in his first three Minor League seasons. He went 2-1 with a 1.96 ERA in 11 starts between the Nationals' Rookie-level Gulf Coast League affiliate and Class A Short Season Auburn in 2013. He was 10-2 with a 2.20 mark in 20 South Atlantic League games with Class A Hagerstown last year.

The 20-year-old fanned 110 batters and issued 28 walks over 98 frames, and it was only his innings limit which stopped him going deeper into games. Just two-and-a-half years removed from Tommy John surgery, Giolito pitched five or fewer innings in 14 games and only pitched into the seventh once, despite taking a shutout with three or fewer hits through six innings on four different occasions.

The team reported Giolito would not be ready for Opening Day on April 7, when Harris said the club wanted to monitor him from a physical perspective. At the time, Harris also said Giolito would likely log around 100 innings this season, similar to his 2014 workload.

Lopez, 21, is in his fourth year of pro ball. He has a career 2.17 ERA over 23 games, including 18 starts. In 2014, the right-hander went 7-3 with a 1.08 ERA in 16 appearances. The 6-foot native of the Dominican Republic struck out 70 batters over 83 1/3 innings and held opponents to a .149 batting average.