James Brewer was asked how many snaps he has taken this summer at left guard. He did not have to think long and hard. “Zero’’ he said. “I haven’t been on the left side since last preseason when they had me do some left tackle.’’ Brewer added he never played on the left side of the offensive line in college at Indiana. So naturally Brewer will be the starting left guard for the Giants in their preseason finale against the Patriots tomorrow night. This will be a big night for the third-year lineman who has yet to prove much of anything. Injuries to center David Baas and right tackle David Diehl prompted several shifts to the lineup. Jim Cordle did not pass the test at center against the Jets and the latest line iteration has Kevin Boothe at center and Brewer coming off the bench to move into Boothe’s left guard spot. Rookie Justin Pugh remains at right tackle. Drafted in the fourth round in 2011 as a possible right tackle of the future Brewer is trying to show he is versatile enough to play multiple positions. If Baas isn’t back for the season opener Brewer could be the starting left guard. Brewer said offensive line coach Pat Flaherty “feels I’m actually a natural at left as far as my footwork technique and how I bend so if he’s confident in me then I’m confident in it as well.’’