Gerrymandering really does not present any sort of a problem in the Senate. It only presents a problem in the House of Representatives and in state legislatures.
The reason for this is that districts for the Senate cannot be gerrymandered. Each Senate seat represents an entire state. The boundary lines for the states have essentially not changed since the states were created. Therefore, it is not as if any party can change them to create a political advantage for themselves.
Gerrymandering does affect the House of Representatives and state legislatures. That is because the lines for these districts are redrawn every 10 years when the census is taken. This sets up a situation where the party in power when redistricting occurs may be able to gerrymander. But this does not affect representation in the Senate in any way.