PITTSBURGH -- The Chicago Cubs aren't getting much return on their investment in Edwin Jackson.
The right-hander lost again Thursday, giving up four runs in three innings as the Pirates beat the Cubs 4-2 at PNC Park to complete a three-game series sweep.
Jackson (1-7) was rocked for four runs and six hits in three innings. He did not return after a one-hour, 47-minute rain delay in the fourth inning.
Jackson had pitched decently in his previous two outings, allowing five runs in 12 innings while going 1-1. He also had six strikeouts against the Pirates and only one walk.
Yet after being signed a to four-year, $52 million contract during the winter as a free agent, Jackson has a 6.11 ERA through 10 starts.
Andrew McCutchen had three hits and two RBIs to help the Pirates to their fourth straight win, pushing a season-high 11 games above .500 at 29-18. Starling Marte added two hits.
Vin Mazzaro (3-0) pitched 2 1/3 innings in relief of starter Jeanmar Gomez for the win. Gomez gave up one run and three hits in 3 2/3 innings.
Jason Grilli notched his 19th save in as many chances by pitching a perfect ninth.
Marte singled and scored in each of the first two innings as the Pirates opened a 4-0 lead.
Marte led off the first with a single, stole second and scored a single by McCutchen. After McCutchen stole second, Michael McKenry hit an RBI single.
In the second, Marte singled with two outs and scored on Travis Snider's triple. McCutchen then drove in Snider with a single.
The Cubs held the Pirates scoreless the rest of the way but managed just two runs.
Chicago's David DeJesus led off the fourth with a double and scored on Anthony Rizzo's groundout. In the seventh, pinch-hitter Ryan Sweeney hit an RBI single that drove home Welington Castillo, who walked.
NOTES: The Pirates plan to wear Pittsburgh Penguins jerseys while traveling on their two-city road trip that begins Friday night at Milwaukee and includes a stop in Detroit. The NHL's Penguins hold a 3-1 lead over Ottawa in their best-of-seven Eastern Conference semifinal series in the Stanley Cup playoffs. ... RHP A.J. Burnett (3-4, 2.57) is scheduled to pitch for Pittsburgh on Friday night against RHP Marco Estrada (3-2, 5.44). ... Chicago RHP Scott Feldman (4-3, 2.19) will try to run his winning streak to five games on Friday night when he pitches against Reds RHP Bronson Arroyo (4-4, 3.28) at Cincinnati in the opener of a three-game series.