Bryan Harper is having the best season of his professional career.

WASHINGTON -- Nationals left-hander Bryan Harper, Bryce Harper's older brother, is having the best season of his professional baseball career. Entering Sunday action, he has a combined 2.36 ERA for Class A Potomac and Double-A Harrisburg. It helps that Bryan Harper is repeating his delivery and commanding his fastball much better.

Bryan, who was selected in the 30th round of 2011 First-Year Draft, had a rough time the previous two years with a combined 5.60 ERA.

"I'm very excited for him," Bryce said. "He has worked hard his whole life. The last couple of years were a little rough for him, but he has been throwing great. He was throwing great toward the end of last year and he threw great during the first half with Potomac.

"He looks like the old Bryan. He looks like he did when he was a senior in high school and [college]. He is doing a great job, doing his own thing. He is really succeeding. He is a 6-6 lefty. They are always going to be good."

Bryan is not only a reliever, he has a handlebar mustache that resembles Rollie Fingers.

"I don't think he is going to get rid of it. He is doing well with it," Bryce said. "He grows a big beard during the offseason, so he was trying to do something different with the Rollie Fingers' mustache. He is doing well with it. I don't think it's going anywhere soon."

Harper ready for rehab assignment

ATL@WSH: Harper takes first BP since surgery

WASHINGTON -- Nationals outfielder Bryce Harper said he is ready to begin his rehab assignment which starts Monday with Class A Potomac. He will play at least two games for Potomac and be re-evaluated after that. Harper will be playing all three outfield positions during his rehab assignment.

The Nationals have yet to confirm that Harper is starting the rehab assignment Monday.

Harper most likely will be rejoining the Nationals when they return home on June 30 against the Rockies.

After missing almost two months of action because of a ligament tear in his left thumb, Harper is pleased that he will play baseball again.

"I'm very excited to get back out there," Harper said. "We'll see where I'm at physically. I'll try to go day by day, at-bat by at-bat. I try to work hard and get back where I need to be."

So far, it looks like Harper is back where he needs to be -- at least in batting practice anyway. During two batting practice sessions this past week, Harper was hitting monster shots over the wall at Nationals Park. Those sessions made him believe that he was ready for a rehab assignment.

"We'll see what I can do against Minor League pitching down there," Harper said. "I'm just excited to get down there and succeed with anything I do. I'll try to get back [to the Major Leagues] as ready as I can be."

Once Harper is back in the Majors, he will help balance a Nationals lineup that needs an extra left-handed hitter. Asked if he knows how much he is missed in the lineup, Harper said, "I try to go out there and play. I try to be a game changer every night and help this ballclub win. I try to go out on the right foot. I try to play as hard as I can and get this team going. … Hopefully, I can come back and do what I did my first year and the second half [of last year]."

At the time of his injury, Harper was hitting .289 with one home run and nine RBIs for the Nationals.