Henry Rodriguez, placed on the 15-day disabled list on June 7, will likely finish his rehab assignment at Double-A Harrisburg, as the Nationals want the right-handed pitcher to be closer to Washington D.C..
Rodriguez, nursing a strained right index finger, pitched one inning of no-hit ball for Triple-A Syracuse on Sunday night.
"I think he's close to being ready," Johnson said. "We're not concerned about his [health]. We want to see him go back-to-back. He pitched last night and threw the ball exceptionally well."
Stephen Strasburg made his first career start at Coors Field on Monday. In one other game pitched at high altitude, Strasburg gave up four earned runs in five innings at Atlanta's Turner Field (1,050 feet above sea-level).
"He doesn't like to get hit no matter what ballpark he's in, whether it's Fenway or any of the other hitting parks," Johnson said.
The Rockies have swept the Nationals six times since the 2005 season. Among National League teams, the Nats' lowest win percentage comes against the Rockies (.327).