PHILADELPHIA -- Sitting in his office just 90 minutes before the first pitch of Sunday's series finale, Nationals manager Dave Martinez heaped praise on veteran right-hander Anibal Sanchez for the way he always "keeps us in ballgames."

Sanchez did exactly that on Sunday, though the Nationals' comeback attempt fell just short in a 4-3 walk-off loss to the Phillies at Citizens Bank Park.

Filling in for the injured Max Scherzer, Sanchez battled his way through six innings for the seventh time in eight starts since coming off the injured list. Nobody would have confused him for the National League strikeout leader -- Sanchez had just two whiffs against the Phillies -- but he breezed through the first eight batters he faced before allowing his first baserunner on a two-out double by Phillies starter Jake Arrieta in the third.

• Box score

Yet after allowing just the one baserunner through his first three innings, Sanchez yielded five hits, two walks and three runs over his final three frames.

"Today, my command early in the first three innings, was really good," Sanchez said. "Later on, I was fighting with my command, but in the end, it’s just about making the right pitch to get out of the jams."

Despite the extra traffic in his later innings, Sanchez still delivered the "right pitch" when he needed to most. With the Nationals trailing 2-1 in the fifth, they elected to intentionally walk Bryce Harper to load the bases with two outs for Rhys Hoskins, who had hit a go-ahead homer in the sixth inning against Sanchez in his April 8 outing in Philadelphia. Sanchez won the battle this time around, getting Hoskins to fly out to strand the bases loaded.

"That was huge," Martinez said. "When Sanchez goes out there and pitches, he’s gonna compete. I liked the matchup right there with Hoskins, and he got a fly ball and got out of the inning."

That kept the Nationals within striking distance through six innings, and Howie Kendrick and Trea Turner delivered consecutive RBI singles to tie the game at 3 in the top of the seventh.

Unlike in Saturday's comeback victory, however, the Nationals were unable to finish off the rally. Washington's final six batters struck out before Phillies third baseman Maikel Franco hit a walk-off homer off reliever Matt Grace with one out in the ninth. That was the only run allowed by the Nationals' bullpen over 8 1/3 innings of work in the three-game series.

Still, the Nats left Philadelphia with their fifth straight series victory -- and a 1 1/2-game lead over the Phillies for second place in the NL East.

"Hey, we battled back," Martinez said. "We were down, we battled back, and Sanchez kept us in the game. [We] came here and won two out of three."

Aside from Scherzer, no Nationals starter has been better of late at keeping his team in the game than Sanchez. He has a 2.47 ERA in eight starts since returning from his strained left hamstring, helping the Nationals' rotation put up a Major League-best 2.98 ERA dating to May 25. Sanchez's ERA is more than a full run better than both Patrick Corbin (3.56) and Stephen Strasburg (3.75) during that stretch.

"I’m always trying to be on the mound and be able to give the team a chance to win," Sanchez said. "That’s my thought every time when I’m on the mound, especially in the division and in the situation we are in right now. We’re in a pretty good stretch, and the team still played really good. At the end, we had a really tough series, but a good series."