The oddsmaker has overreacted to no Dak Prescott with this low of a total. 

Cooper Rush is a serviceable backup quarterback. He's not a stiff. He has skill position talent to rely on. Ezekiel Elliott looks much better than he did last season. Tony Pollard is a home run threat and drawing more playing time. The Cowboys also get back Michael Gallup to upgrade their wide receiving corps. The Giants aren't likely to have Leonard Williams, their best defensive lineman. 

The Giants are far more credible on offense under Brian Daboll. New York's offensive line has improved and Saquan Barkley is running the best he has since his rookie season, finally free of injuries. Barkley entered Week 3 leading the NFL in rushing yards.

It doesn't take much in today's NFL, with its rules skewed toward offense, to get above a total less than 40.