In second-half stoppage time, Marshall, moving to his right, somehow changed direction and managed to tip Andreas Weimann's close-range effort behind at the Cardiff City Stadium on Tuesday.
It could prove a crucial save at the end of a season in which Cardiff look destined to be fighting for Premier League survival come May.
And Solskjaer was quick to pay tribute to Marshall, as well as the central defensive pairing of Ben Turner and Steven Caulker.
"I thought it was a goal," Solskjaer told BT Sport.
"But then again you've got David Marshall there so you almost expect him to save it.
"He's been fantastic this season and again he saved us.
"He saved us again but you can talk about Steven Caulker and Ben Turner. They've done a fantastic job, as good a performance as you can ask for."
Turner, who was named man of the match, called on the Cardiff supporters to continue to back the team in their fight to avoid the drop, with the club second from bottom.
"Obviously things haven't been going as well as we want," he said.
"We suffered a disappointing result in the derby, but we need to stick together and we need the fans now more than ever."
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