Montgomery (1-1) combined with four relievers who were perfect for the shutout.

Rizzo had three hits and three RBIs for Chicago, which has won two in a row and three of its last four.

The Pirates, who had just two baserunners and none in scoring position, have lost three straight and eight of 10.

Montgomery allowed two hits, with five strikeouts and no walks. He was perfect through four 4 1/3 innings, before Corey Dickerson singled up the middle before being erased on an inning-ending double play. Montgomery also allowed a leadoff single to Sean Rodriguez in the sixth. The left-hander struck out the next two batters before yielding to reliever Steve Cishek after his pitch count reached 76.

Montgomery made his first start of this season after leading the bullpen in innings. He got the call as Chicago revamps its rotation with Yu Darvish on the disabled list.

Cishek pitched one-third of an inning. Justin Wilson, Pedro Strop and Luke Farrell each pitched one inning.

Pittsburgh starter Chad Kuhl (4-3) gave up one run and four hits in six innings, with five strikeouts and four walks.

It was the 2,500th meeting all-time between the teams, dating to 1887.

Rizzo led off the second with his seventh homer, to right, for a 1-0 Cubs lead. Later that inning, Dickerson robbed Kyle Schwarber of a homer when he reached over the wall in left to make a catch.

With two outs in the seventh, Russell pinch-hit and lined his second homer to left. Albert Almora Jr., who had singled, also scored for a 3-0 lead.

Chicago tacked on two more in the eighth when Chris Gimenez grounded into a bases-loaded forceout, but two runners scored on catcher Elias Diaz's throwing error. Pittsburgh manager Clint Hurdle was ejected for arguing that Rizzo went out of his way to make contact with Diaz on the force play at the plate.

Rizzo added a two-run single in the ninth.

--Field Level Media