United cannot afford defeat in Switzerland if they're to progress to the knockout phase.
"We probably should have killed the game off," he added. "We had chances in the first half and second half but we're happy with the clean sheet and the performance.
"I suppose it is in the back of your mind [that City had already won and extended the lead at the top to eight points]. But we're focused on what we've got to do and, when we cross that white line, we're only in control of what we can control. The gaffer said we'll take ten 1-0 wins if we win the league so that's what we're doing."