At 4-6, the Chargers do not have many more losses to give. Most playoff teams are required to be 10-6, although a 9-7 record could possibly allow the Chargers to squeak through into the playoffs.
To see the Chargers playoff odds and determine their chances with each win or loss, check out this season simulator from the New York Times. You will see that the Chargers can likely afford one loss, but that loss cannot come against the Kansas City Chiefs or Oakland Raiders, meaning there are three must-win games remaining.
In the remaining six games, every team the Chargers will face is tough but beatable.