The 42-year-old was very happy with the Bundesliga side's win over Steaua Bucharest in their European opener, feeling that they dominated proceedings throughout the game
Second-half goals from Atsuto Uchida, Kevin-Prince Boateng and Julian Draxler were enough to secure a comfortable victory for the Bundesliga side and their boss hailed their perfect start to their European campaign.
"We have managed a perfect start to our Champions League season. I'm extremely happy we kept our third consecutive clean sheet," Keller said at a press conference.
"We played well in the first 30 minutes, where we built a lot of pressure and created one or two chances, and, from the 60th minute, we clearly dominated the game and eventually got some good goals. I am proud of the team."
Schalke now sit at the top of Group E on goal difference, level on points with Basel, who secured a surprise 2-1 win over Chelsea at Stamford Bridge.