Diamondbacks 5, Pirates 1: Joe Saunders pitched seven strong innings as Arizona pulled away from a struggling Pittsburgh club to remain unbeaten at home.

The Diamondbacks took the lead for good when Ryan Roberts delivered a two-out RBI single against Erik Bedard (0-3) in the fourth inning. Arizona then used a pair of homers to pull away, as Chris Young belted a two-run blast to left in the sixth against Evan Meek and pinch hitter Gerardo Parra added solo shots in the seventh off Chris Resop.

Saunders (1-0) got the win, striking out five while scattering six hits and two walks.

Bedard suffered his third consecutive tough-luck setback, allowing two runs on three hits over five innings of work. He struck out three and walked four.

Neil Walker’s RBI single gave Pittsburgh a 1-0 lead in the top of the first, but Arizona drew even in the bottom of the inning on Aaron Hill’s solo home run.

The Pirates have totaled just 19 runs this season, easily the lowest total in the major leagues.

GAME NOTEBOOK: The Diamondbacks are 4-0 at Chase Field, making them one of just two National League clubs still perfect on their home field ... Saunders has allowed just one run in 14 innings this season (0.64 ERA) ... The Pirates have scored one run or fewer in five of their seven losses.