Gabriel left the pitch in tears in the 23rd minute after appearing to accidentally injure his knee when he slipped as he tried to control the ball minutes earlier.
City midfielder Kevin De Bruyne was also injured against Palace.
But Belgium worldwide De Bruyne was seen walking back to the City dressing room accompanied by two medical staff. In two days, we have another game (at home to Watford).
"We were lucky in the recent games, and today we will see", Guardiola told reporters. "We were lucky against Tottenham and against Newcastle".
That City performed below the extraordinary level they have consistently achieved this season meant that they dropped points in the Premier League for only the second time in 21 games, and for the first time did not score.
Ederson ultimately saved the spot-kick to preserve City's unbeaten run and, while some have accused the Palace winger of going down too easily, Guardiola was content to take the word of referee Jon Moss.
Guardiola would not comment on the decision to award the penalty, which came after Wilfried Zaha went down under a challenge from Raheem Sterling. "But if the referee decides it was, then that's okay".