Can Nationals' starter Doug Fister find his sink?

In six starts since he returned from over a month on the DL, Washington Nationals' right-hander Doug Fister is (1-4) with the Nats 1-5 in his outings, over which the 31-year-old starter has put up a 4.72 ERA and a .324/.362/.479 line.

Fister went just five innings last night in the series opener in Pittsburgh's PNC Park, giving up nine hits and four runs before he was lifted with the Nationals down 4-1 to the Pirates in what ended up a 7-3 loss.

Starling Marte hit an RBI triple to left in the first to drive Andrew McCutchen in, taking a hanging 2-2 curve to the left-center gap.

Pedro Alvarez homered on a line drive to left in the second, sending an 87 mph 1-1 fastball outside into the left field seats.

Jung Ho Kang lined a 3-1 cutter to right in the fifth for an RBI double then scored on a groundout to the mound by Alvarez.

Fister finished out the inning, but was up to 99 pitches and Nats' skipper Matt Williams went to the bullpen after that, bringing Tanner Roark on in relief.

"The curveball to Marte in the first was not where he wanted it," Williams said in discussing Fister's outing after the Nationals' 7-3 loss.

"It just hung up in the zone. And then the homer to Alvarez was just kind of out, over. He's not getting the sink that he normally gets. It's running but it's not sinking. Of course his last one, he got behind and hung a -- it was a cutter, but it was just up in the strike zone, so and then of course, he gets the pitch he wants to and the ball is not hit hard enough to keep the guy at third base, so encapsulates his night pretty much right there, just nothing is going right for him."

"'It’s inexcusable,'" Fister told reporters, including the Washington Post's James Wagner.

"'Starting to get back to feeling better and strong and being able to locate. But missing on too many pitches over the plate. I’m not going for the right pitches at the right time. Not going after them and going with my second- or third-best pitch. I’ve just got to reevaluate myself.'"

Fister said he's struggling to get his "true sinker back" and he's working on, "'... being able to keep it down and keep the ball moving downward.'"

"It's just not sinking the way he wants it to," Williams said. "And with Doug he's got to have that movement and if it's going laterally it's not as effective."

"He'll got a couple of innings where he's able to work through and make the pitches he needs," Williams explained, "but there are other innings where it just kind of flattens out on him. So he'll continue to work on it."

"With a sinker ball pitcher, if he loses feel for that then it's hard for him to make mistakes in the middle of the plate, because it's 87 or 88 mph instead of 96. So he'll continue to work."

His ground ball percentage is down from 54.3% in 2013 and 48.9% in 2014 to 41.2% so far this season in 74 innings pitched. His batting average on balls in play is up from .262 in his first season in D.C. to .317.

Desmond connect for 100th career home run

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His line drive percentage is up from 16.9% last season and a 20.2% career mark to 24.6%.

So what if anything does he need to do? Is there an identifiable problem? Or fix?

"He needs to get on top of the baseball and turn the hand over to get it to sink," Williams said. "For some reason he's just not feeling it. He hasn't felt it. He's been able to change speeds fine. He's healthy. Velocity is normal last couple of times out. It's not anything drastic off, he's just getting it to where he wants it to get to with the movement he wants, so he'll continue to work."

Can Doug Fister get back to being Doug Fister? How long can the Nationals stick with him if he can't?