WASHINGTON -- A day after pitching for Class A Potomac, Nationals closer Chad Cordero was informed Thursday that he will have another rehab assignment Friday for Potomac.

If things go well for him Friday, Cordero most likely will be taken off the disabled list by Sunday. Cordero has yet to pitch in a Major League game because of right shoulder tendinitis.

On Wednesday, Cordero's fastball was clocked at 87 mph, which is a couple of digits below what he normally throws. He pitched one scoreless inning, giving up one hit and striking out one in a 4-3 victory over Myrtle Beach.

"He had good command, we just want to see him one more time out there," manager Manny Acta said.

Cordero said his arm felt fine, he didn't experience any pain and was able to throw his slider for strikes. In fact, his strikeout came on a slider.

"I was able to throw everything that I needed to throw and I didn't have any pain," Cordero said.

Meanwhile, outfielder Wily Mo Pena continues to recover from a left oblique strain. On Thursday, he went 3-for-3 in an extended spring game.

Pena will play one more extended spring game on Friday and then go to Triple-A Columbus to start a rehab assignment the next day. The Nationals are hoping that Pena can start playing in Major League games by late next week.

Bowden expressed how much Pena and outfielder Elijah Dukes are missed in the starting lineup. Dukes is on the DL because of a right hamstring strain. They could possibly be the difference-makers who could provide protection for Ryan Zimmerman.

"Pena and Elijah are missed because every time they come to the plate, they have a chance to hit the ball out of the ballpark," Bowden said. "And whether they do or they don't, the threat in the lineup allows better pitches for the people around you when you have that threat all the time.

"When you lose three one-run games and another game that went into extra innings, that's one swing of the bat. So sure, [they are] missed."

As for Dukes, don't expect him back in the lineup anytime soon. The Nationals are going to wait until Dukes' hamstring is 100 percent healed.

"He said he feels better and he knows his body, but I don't care," Bowden said. "It's a Grade 2 hamstring [strain]. I had enough experience with Ken Griffey Jr. in Cincinnati with the hamstring. I take the hamstrings extremely seriously, and I'm not going to have Dukes out all year because we didn't do a good job of allowing the hamstring to heal."