After trading 10-3 victories in the first two games of the series, Trevor Williams faces off against veteran Jeff Samardzija at 3:45 p.m. Eastern
The Pirates will rest David Freese in favor of Adam Frazier, and John Jaso will attempt to play right field in place of the winded Jose Osuna.
The Giants will send five left-handed batters up against Williams.
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PIRATES
1 R Starling Marte, LF
2 R Josh Harrison, 3B
3 R Andrew McCutchen, CF
4 S Josh Bell, 1B
5 L John Jaso, RF
6 R Francisco Cervelli, C
7 L Adam Frazier, 2B
8 R Jordy Mercer, SS
9 R Trevor Williams, P
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GIANTS
1 L Denard Span, CF
2 L Joe Panik, 2B
3 L Brandon Belt, 1B
4 R Buster Posey, C
5 L Brandon Crawford, SS
6 R Hunter Pence, RF
7 L Conor Gillaspie, 3B
8 R Gorkys Hernandez, LF
9 R Jeff Samardzija, P