Nolasco may be switched to throwing in a simulated or Minor League game Wednesday.
Olsen is recovering from shoulder tendinitis that has kept him out of Grapefruit League games since March 2.
In two spring starts, the lefty has posted five scoreless innings. But he was scratched from a March 6 start against the Cardinals, and he's been recovering since.
On Sunday, Olsen threw in a controlled setting against two hitters: right-handed hitting Jason Wood and lefty-batting Dallas McPherson.
The two batters switched on and off, giving Olsen looks against hitters from both sides of the plate. After Olsen struck out McPherson to start off the simulated game, Wood lifted a fly ball to center field.
The only run Olsen allowed came in McPherson's next at-bat. The power-hitting third baseman, who is recovering from a groin problem, belted a home run to right-center.
Immediately after throwing the pitch, Olsen knew he had hung a pitch and blurted out "Oh, no!"
Olsen had one strikeout, two hits allowed, and he induced four fly-ball outs. He didn't walk a batter.
Manager Fredi Gonzalez observed and noted Olsen is on track to join the rotation when the season starts.
"He will pitch in a game [Thursday], if everything goes well," Gonzalez said. "He threw well. He threw strikes."
The Marlins simulated a baserunner as well, so Olsen threw out of the stretch as well as the windup.
The plan now is for Olsen to be off Monday and throw on the side Tuesday. He again will be off Wednesday and hopes to get into the game Thursday.
By pitching Thursday, Olsen lines up to be the Marlins' fourth starter when the season opens. If he continues throwing every fifth day, he would slot into starting April 4 against the Pirates at Dolphin Stadium.
Prior to his bout with tendinitis, Olsen was projected to be Florida's Opening Day starter. Now, the team has yet to announce who will take that ball that day against the Mets.
Veteran Mark Hendrickson, who will start again on Tuesday against the Dodgers in Jupiter, is regarded as the front-runner to face the Mets, who will be starting Johan Santana.
Hendrickson will throw again Tuesday against the Dodgers in Jupiter. Burke Badenhop, a surprise candidate in camp who is vying for either a starting or relieving job, also will pitch that day.