PITTSBURGH -- Despite these being the waning days of the season, both teams will have an extra source of motivation when the Washington Nationals and Pittsburgh Pirates open a weekend series Friday at PNC Park.

The Nationals (89-63) are on the verge of clinching the National League East title. Their magic number is two, so they could wrap it up as soon as Friday with a win and a New York Mets loss to Philadelphia.

While locking up its third NL East title in five years has seemed like a formality for some time, Washington might have wrapped up the division earlier if not for a four-game losing streak that it broke Wednesday with an 8-3 win at Miami.

The Nationals were off Thursday and will be playing their final road series of the season.

Pittsburgh, meanwhile, seemed to blow its shot at an NL wild-card spot when it lost eight in a row and 12 of 14 beginning in late August. However, the Pirates have used a resurgence to keep their postseason chances alive and render each game the rest of the way critical.

Before their 3-1 loss Thursday at Milwaukee, they had won six of seven and seven of nine. They are at .500 (76-76) and were four games out of the wild-card chase, pending a late San Francisco game Thursday, with 10 games remaining.

To take advantage of their slim shot at the postseason, the Pirates will need to improve at home. Heading into their final homestand, a seven-gamer against division leaders Washington and Chicago, they are 2-9 in their past 11 home games, 3-13 in their past 16 to fall to just two games over .500, 36-38, at PNC Park.

Pittsburgh won't have to face 18-game winner Max Scherzer, a potential Cy Young candidate, this weekend.

Friday, Gio Gonzalez (11-10, 4.48 ERA) will attempt to continue his streak against the Pirates. He has made seven career starts against them and has never lost, going 4-0 with a 2.81 ERA. He has never given up more than three earned runs against Pittsburgh.

Gonzalez is coming off a tough-luck loss, his first loss in nine starts. He gave up six runs on nine hits in 4 1/3 innings Saturday in a 7-3 loss to Atlanta, striking out seven and walking none.

Only one of those hits was for extra bases, and several were soft singles.

"Gio was at his best. He made some good pitches," manager Dusty Baker said, according to the Washington Post. "I mean, you didn't see those balls blooping in there and stuff? You can't do anything about that."

It seems likely Pittsburgh at some point this weekend will face Washington closer Mark Melancon, who returns to PNC Park for the first time since the Pirates traded him to the Nationals before the trade deadline. Melancon is 12-for-12 in save opportunities with Washington.

With the Nationals, though, Melancon has not been saved solely for save situations -- including Wednesday, when he pitched the ninth despite the lopsided score.

"I had not been used prior to this in non-save situations like I have, and I don't want to be (unavailable) when there is a save situation," Melancon told the Washington Post this month. "Even in a tie game, I feel like I want to be able to contribute there. That's been different a little bit."

The Pirates on Friday will counter with rookie starter Jameson Taillon (4-4, 3.39 ERA), who has not faced Washington.

Taillon has allowed three earned runs or fewer in 13 of his 16 big-league starts, and two runs or fewer in nine starts.

After being skipped in the rotation to manage his innings and perhaps being a bit rusty, Taillon gutted through five innings Saturday, giving up three runs on nine hits in a 10-4 win at Cincinnati.

"What you got to see was a guy go out there not having his 'A' game and still finding a way to compete at this level against a team that swings the bat very well at this ballpark," manager Clint Hurdle said, according to MLB.com.