Die Knappen's season began to derail in November, as they picked up just seven points between then and midway through February.
Manager Huub Stevens was sacked in the midst of the run, while the team's Champions League hopes lay in tatters.
However, a run of five wins in the last seven games has seen them re-enter the top four.
"I'm incredibly proud of how my team got back into the game and turned it around," Sky Sports News quotes Keller as saying.
"We are very happy with this point, which cements fourth place. That was the priority when I took over as coach here."
Schalke's last match saw them draw 2-2 with third-placed Bayer Leverkusen.