Was GW's recent loss expected or did they underperform? I like to bet on teams that underperformed the last time out because the public puts too much emphasis on a team's most recent performance when capping games.
Who did the Stags beat and why did they win (i.e., did they shoot better, play better defense, out-rebound their opposition)? Once you have that answer, ask yourself whether they can do the same thing to GW.
Not trying to be a dick, but there is a TON more to consider here.