The left-hander will seek to win back-to-back starts for the first time this season in Sunday's series finale against the Chicago Cubs, who will try to help Scott Feldman earn his fourth victory in as many outings.Harper sat out a second straight game Saturday as he continues to recover from surgery for an ingrown toenail, and Jayson Werth was placed on 15-day disabled list, retroactive to May 3, because of a strained right hamstring.Manager Davey Johnson said he had expected Harper to return to the lineup Saturday, but his toe was still ailing.Without those two players, the Nationals (20-16) took Friday's series opener 7-3 but fell 8-2 the next day to end a five-game win streak. Anthony Rizzo, batting .448 with 14 RBIs in his last 15 games, had three hits and drove in a pair of runs as the Cubs (14-22) snapped a five-game skid in the series.Gonzalez (3-2, 4.97 ERA) will try to help his team bounce back with his third win in four starts. He gave up two runs over six innings in a 6-2 victory in Pittsburgh last Sunday after allowing five over four frames in a loss in Atlanta on April 30."Gio did a great job of keeping us in that game after the tough start," Johnson said.Gonzalez tossed seven scoreless innings and struck out nine in his most recent start against the Cubs, a 9-1 home win Sept. 5. He was 0-1 with a 10.38 ERA in his previous two matchups, both in Chicago.In this one, he'll throw opposite Feldman (3-3, 2.70), who is 3-0 with a 1.59 ERA in his last three starts. The right-hander gave up two hits and a walk over seven scoreless innings Monday in a 9-2 win over his former Texas teammates."That's really encouraging to see. That's three or four really good outings in a row, especially two very impressive outings in a row," manager Dale Sveum told the team's website. "He's got a feel for (his cutter) right now and it's impressive, especially to go along with his two-seamer."In his first matchup with Washington, Feldman will try to earn wins in four straight starts for the second time in his career. He pulled off that feat Aug. 23-Sept. 9, 2009, while with the Rangers.Only two Nationals hitters have had more than one at-bat against Feldman. Kurt Suzuki is 5 for 17 (.294) with two doubles, and Denard Span is 4 for 14 (.286).Rizzo is 0 for 3 with two strikeouts against Gonzalez, while Starlin Castro and Julio Borbon are both 4 for 7.