The Belgium international returned from a thigh injury and played the full 90 minutes as City beat West Brom 3-2 on Wednesday.
Pellegrini has a slight concern over whether Kompany can manage two games in quick succession but insists the defender is available for selection.
"Vincent is OK, but we will see if he can play two matches in four days," he said on Friday.
"He finished the last game without any problems.
"We will see how he recovers but I don't think it's a great risk to play him again."
Pellegrini will be without David Silva, Stevan Jovetic and Matija Nastasic however, although the former could be back in action after the weekend.
"I think on Monday David Silva will be ready. We'll see after this weekend and how he is then," the Chilean added.
"Stevan Jovetic and Matija Nastasic are also still out.
"It was an important three points for us at West Brom. We must continue that against Southampton."
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