The remaining five states are Alaska, Arizona, Georgia, Nevada, and Wisconsin. Of those states, Alaska is a Republican shoo-in while Democrats are likely to retain Arizona - even if the seat is expected to be tightly contested. The latter won't be as close as Pennsylvania though and the result there was already a major blow to the Republicans this time.
Meanwhile, Wisconsin is another tight one but that seems to be slightly Republican favoured at the moment with Ron Johnson leading with 50.7% against Mandela Barnes at 49.1% with 93% of expected votes counted. That just leaves us with Georgia and Nevada as the final two states with a projected result of 49-49, after accounting for the others.
As such, Nevada is where Republicans really have to make a stand and pull through if they are to have any chance of gaining control of the Senate. It will be a race between Catherine Cortez Masto (D) and Adam Laxalt (R). The polling average coming into voting day suggests that Laxalt holds a narrow advantage.
With Republicans having now lost out on Pennsylvania, their only two best shots to gain control of the Senate are going to be Nevada and/or Georgia. The latter is pretty much a coin flip as it looks set for another run-off on 6 December instead. So, this makes Nevada as a pivotal battleground in this year's race.