After clinching their fourth straight series victory, the Pittsburgh Pirates vie for their first sweep of the season on Thursday as they conclude a three-game set versus the visiting Arizona Diamondbacks. Rookie Gregory Polanco belted a two-run homer to extend his torrid stretch of reaching base to 19 in 21 games as Pittsburgh cruised to a 5-1 triumph on Wednesday. Starling Marte, who had an RBI double in the contest, has hit safely in all 12 games in his career versus the Diamondbacks.Paul Goldschmidt and Aaron Hill are enjoying strong series, but Arizona is mustering little else en route to losing three in a row. Goldschmidt, who is leading the National League in All-Star Game vote totals at first base, collected three hits to improve to 5-for-7 in the set. Hill recorded an RBI single for the second straight game Wednesday.TV: 7:05 p.m. ET, FSN (Arizona), ROOT (Pittsburgh)PITCHING MATCHUP: Diamondbacks RH Brandon McCarthy (2-10, 5.11 ERA) vs. Pirates RH Vance Worley (2-0, 1.74)McCarthy posted his first win since May 3 as he allowed one run and struck out seven in as many innings of a 2-1 triumph over San Diego on Friday. The 30-year-old, who did not walk a batter for the first time in five outings, owns a road record of 2-4 - which is significantly better than his 0-6 mark at home. McCarthy has struggled when facing Pittsburgh, posting an 0-2 record with a 5.40 ERA while allowing the Pirates to bat .304 against him. Worley recorded his third straight quality start by yielding one run on seven hits in as many innings of a 5-2 victory over the New York Mets on Thursday. The 26-year-old continues to have impressive control, issuing just three walks in 20 2/3 frames this season. Worley has fared well in two career meetings with the Diamondbacks, going 1-0 with a slim 1.00 ERA and 0.78 WHIP.WALK-OFFS1. Pittsburgh CF Andrew McCutchen, who was named the National League Player of the Month for June, has hit safely in all but one of his last 10 games.2. Arizona manager Kirk Gibson reiterated that RHP Addison Reed would remain the team's closer despite failing to convert a save opportunity for the fourth time in 23 opportunities in the series opener.3. Pirates C Russell Martin is 3-for-6 with a double since returning from a two-game absence due to a sore left shoulder.PREDICTION: Pirates 4, Diamondbacks 1