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4/22/2014 6:30 P.M. ET

Nats team up with EPA, Coca-Cola for Earth Day

WASHINGTON -- The Nationals teamed up with the Environmental Protection Agency (EPA) and Coca-Cola to celebrate Earth Day at Nationals Park on Tuesday, when they hosted the Angels.

EPA deputy administrator Bob Perciasepe threw out the ceremonial first pitch and also participated in an interview that was shown pregame on the video board. Also shown were a public-service announcement from the EPA promoting action on climate change, and trivia segments in honor of Earth Day and promoting recycling and other green strategies. The popular Presidents Race also was set to incorporate a pro-recycling message.

In addition, members of the Young Activist Club made up the night's Starting Nine -- who meet Nationals starters at their positions before the first inning -- as well as the announcer of the traditional "Play Ball," before first pitch. The Young Activist Club is a student group from Takoma Park, Md., trying to get rid of Styrofoam and other polystyrene to make their community a more green and safe place to live.

Coca-Cola's recycling education vehicle also was parked in front of the center-field gate, offering fans information about recycling as they entered the ballpark.

Barrett recalled, back in Nationals' bullpen

WASHINGTON -- When the Nationals optioned rookie reliever Aaron Barrett to Triple-A Syracuse on April 12 in order to clear space for a fresh arm, he knew he'd have to remain there a minimum of 10 days. As it turned out, his stay in the Minors didn't last any longer than necessary.

The Nats reshuffled their bullpen again on Tuesday, recalling Barrett from Syracuse on the first day he was eligible to return, and optioning lefty Xavier Cedeno to Triple-A.

"It was a little bit of a shock," said Barrett, who arrived in time for Tuesday's game against the Angels. "I know they told me it had to be 10 days, but at the same time, did I really expect it to be on the 10th day? Not really. I was just going down to Triple-A and expecting to get my work in, and if it happened, it happened. Just glad to be here."

Barrett made the Opening Day roster after a strong Spring Training and continued to make a good impression on manager Matt Williams, who entrusted him with some important assignments. The 26-year-old pitched 4 1/3 scoreless innings over six appearances, giving up only one hit and two walks while striking out six.

When the Nats sent him down, it was only the result of a relief corps that had been taxed by the club's starters having some short outings.

"From what I've seen in every situation we've put him in, he's aggressive and he's commanded the zone, and gone after hitters," Williams said of Barrett. "I wouldn't expect anything else from him. That's just his mentality."

Barrett spent all of last season at Double-A Harrisburg, notching 26 saves with a 2.15 ERA.

Due partially to some bad weather, Barrett only pitched in two games at Syracuse since being sent down, the most recent on Saturday. He gave up two hits, walked one and struck out two over 2 1/3 scoreless innings.

Cedeno, who has see-sawed between Syracuse and Washington over the past two seasons, appeared in his first game of the season on Monday against the Angels, giving up two hits over 1 1/3 scoreless innings. With Barrett replacing Cedeno, the Nats are back to having two lefties -- Jerry Blevins and Ross Detwiler -- in their bullpen.

Williams: We'll see how bullpen roles play out

WASHINGTON -- While Nationals reliever Drew Storen went through a rough patch last season, Tyler Clippard was the steady hand in the back of the bullpen, setting up closer Rafael Soriano. So far in 2014, their fortunes have been reversed.

That dynamic was on display on Monday night against the Angels. Storen finished off the seventh inning by retiring Mike Trout with a man on base, but Clippard couldn't hold a one-run lead in the eighth. Burdened with Ian Desmond's inning-opening error, he went on to allow four unearned runs, including Raul Ibanez's go-ahead three-run double.

Clippard, with a 2.72 ERA over 337 relief appearances from 2009-13, has allowed a run in five of his 11 games this season, with 14 baserunners over 9 2/3 innings. Storen, on the other hand, has held the opposition to two baserunners and one run over 7 1/3 innings.

Given that situation, might manager Matt Williams change how he deploys his late-inning relievers?

"Really, all three of those guys, in theory, at the back of the bullpen are interchangeable, depending on workload, depending on what happens during the course of a series or during a week," Williams said. "So I expect Drew to be ready to pitch at any point. He can pitch the seventh, he can pitch the eighth, he can close if need be. He's done it before, and had success doing all three.

"Does it change roles? I think that's yet to be determined. We'll see how it all plays out. But he's capable, and he's pitched really well."

So far, Williams has shown consistency with how he's used that trio. Storen has made the bulk of his appearances in the seventh inning, Clippard in the eighth and Soriano in the ninth.

With games on the line in those late innings, any issues can put you under the microscope. Williams said Monday that Clippard has yet to find his changeup and has been inconsistent with his fastball location, and those problems have cost him.

Storen, coming off a season that saw him spend part of his summer at Triple-A Syracuse, certainly can empathize with his good friend and teammate.

"When you're a late-inning bullpen guy, it's going to be magnified quite a bit, because we're coming in with a small lead, and those are the tough ones," Storen said. "It's one of those things, it's a matter of inches, nothing drastic.

"It's human nature and it comes with competing that you want to punch harder. In reality, you've just got to trust your stuff and kind of go with it. That was part of my learning process, that trying harder in this game isn't always trying better."

Fister on track for rehab start on Sunday

WASHINGTON -- Doug Fister took another step in his recovery from a right lat strain on Tuesday, throwing his second simulated game in extended spring training in Viera, Fla. The three-inning, 44-pitch outing went well, according to Nationals manager Matt Williams, and the right-hander is expected to return to Washington on Thursday before making a Minor League rehab start on Sunday.

"Felt good with everything," Williams said. "Lots of grounders, and reported that he felt really good with it."

Fister has been on the 15-day disabled list since March 29, and now has thrown simulated games of two and three innings. The plan is for him to complete rehab starts of four and then five innings before being activated, barring any setbacks.

The location of Fister's assignment has not been set, but Williams said it likely will be Class A Advanced Potomac.

Worth noting

• Williams said that first baseman Adam LaRoche is dealing with some quad soreness, one reason he was out of Tuesday's starting lineup. With the Nats facing Angels lefty Tyler Skaggs, it also was a good opportunity for Williams to give LaRoche a day off and insert right-handed batter Tyler Moore in the lineup. LaRoche was still available to pinch-hit.

• Williams used his 17th different batting order in 21 games -- not including pitchers -- starting Danny Espinosa in the No. 2 spot and Anthony Rendon in the No. 4 spot for the first time this season on Tuesday. Espinosa hadn't hit above sixth in 2014, but has swung the bat well, with a line of .288/.339/.481 entering play. Rendon, meanwhile, now has started in every place in the lineup except third and ninth.

Andrew Simon is a reporter for MLB.com. Follow him on Twitter @AndrewSimonMLB. This story was not subject to the approval of Major League Baseball or its clubs.