(Photo by John McDonnell/The Washington Post)

UPDATE, 6:05 p.m.: Pitching coach Steve McCatty said that Doug Fister looked good in his bullpen session on Friday morning. After four straight days of throwing, he will rest on Saturday morning. If Fister feels good, he could throw two innings in a minor league camp on Sunday, McCatty said. But he was encouraged that Fister could complete his bullpen without issue.

“It’s a positive sign,” McCatty said. “We have to be cautious right now. And just make sure he’s fine. We’ll see how he is (Saturday) morning. Depending how he is, we’ll see when we get him in the game.” –James Wagner

ORIGINAL: Right-hander Doug Fister came away encouraged but not yet prepared to declare himself ready for the start of the regular season after he threw off a mound this morning for the first time since he developed inflammation in his throwing elbow.

Fister had not thrown any pitches since March 2, when he felt elbow soreness in his first spring training start. He threw 25 pitches in his bullpen session, mostly fastballs with a few curveballs and changeups mixed in. Pitching coach Steve McCatty and head athletic trainer Lee Kuntz looked on.

“It was a pretty good bullpen,” Fister said. “Felt pretty good about it. Step in the right direction.”

On Thursday, Fister pitched on flat ground and felt tightness in his arm. He felt improvement this morning, but some of the feeling remained.

“Stiffness,” Fister said. “It’s cold outside. A little tight.”

Fister will wait to map out his next step. “See how we feel the next couple days,” he said. He did not know if the Nationals had any more tests for his elbow planned, but he assumed they did not.

“Threw all the pitches, felt good,” Fister said. “It’s just a matter of getting out there and fighting through whatever.”

Manager Matt Williams said earlier this week that if Fister stays on the Nationals’ plan for him to rebuild arm strength without setbacks, he will be able to take his first turn in the rotation. The Nationals will not require a fifth starter until April 6, so they have ample time. Fister, though, does not want to look that far ahead.

“I’m not going to project that,” Fister said. “It’s a matter of how I feel the next day. We’ll take it day-by-day at this point.”

The Nationals are taking a cautious approach with Fister, whom they acquired this winter in a trade with the Tigers for Steve Lombardozzi, Ian Krol and pitching prospect Robbie Ray.

The Nationals wanted to see how Fister felt today before he even threw the mound session. Before Fister stepped in the bullpen at Space Coast Stadium, McCatty asked him how he felt. Fister assured him he felt better than Thursday.

“No lying,” McCatty told him.

“I wouldn’t lie,” Fister said. And then he walked to the mound, a small relief, for now, for everybody within the Nationals.

“We want to make sure we’re taking care of him for the long term as opposed to his first start,” Williams said. “We have to make sure we progress slowly to make sure we have him for a full season and not rush him too quickly and lose him. All indications are that all things are good, just the soreness and inflammation we need to get out of there.”

● Reliever Ryan Mattheus threw another bullpen session and felt “great.” He will throw live batting practice Monday, and then get into his first game of the spring. Mattheus was shut down earlier this spring with a strain in his chest muscle.

● Third baseman Ryan Zimmerman participated in the Nationals’ workout back in Viera, including some light throwing. Zimmerman has not played since Monday with soreness in his right shoulder. He plans to take a full infield practice and play Saturday in Jupiter, though he said he might be a designated hitter during the game.

● Bryce Harper and Ian Desmond, whom Williams sent home with illnesses yesterday, both took batting practice with the Nationals who stayed back in Viera.