One to play in the midfield, and one as a focal point in attack.
Instead, Goodwin will have to continue making decisions on the run with his versatile game-breaker after Petracca threatened to drag the Demons over the line against Carlton.
Melbourne produced their first scoreless opening quarter since 2008 - and first against the Blues since 1942 - before Petracca was shifted forward.
The 28-year-old superstar responded with a career-best five majors and two goal assists as the Demons fought back from 38 points down before falling agonisingly short in a nailbiter.
"Christian was outstanding," Goodwin said after his side's 12.5 (77) to 11.10 (76) defeat on Thursday night.
"Clearly, he had an exceptional night and had enormous impact for us.
"It was really pleasing for us that we were able to put Christian in a position where he had impact on the scoreboard for us.
"He was one of the main reasons we were able to get back in the game."
Melbourne winger Ed Langdon played a different role forward of the ball and Alex Neal-Bullen spent more time in the midfield as Goodwin looked to cover Petracca's absence around the contest.
"We've just got to adapt on the run and the game demanded that we needed change things up," the coach said.
"Carlton started the game really well ... and we needed to find an avenue to score.
"Some of those adjustments allowed us to do that but we sit here and we're not happy. We come away with a loss that will hurt."
Petracca had started the round-nine contest in his usual midfield role, watched closely by Carlton's Matt Kennedy, who Blues coach Michael Voss later joked had done too good a job and forced his opponent to push forward.
Carlton defenders Nic Newman and Mitch McGovern both spent time on Petracca but struggled to contain him.
Newman had the last laugh when he and Patrick Cripps pinned Petracca holding the ball as the Blues clung to their one-point lead in the dying stages.
"He could've been a real difference for them," Voss said.
"We talk about the collective a lot but that seemed to make a fairly big difference.
"His particular individual performance was pretty special but it did take us as a collective to be able to get the job done."
Despite Petracca's heroics, Melbourne suffered a third consecutive loss to Carlton by less than a goal.
Six of the last eight games between the sides have been decided by single-figure margins.
"We're two teams that value similar things and every time we play Carlton, we know it's going to be a fight," Goodwin said.
"It's going to be close, it's going to be a battle and it's generally going to be low scoring.
"I think we'll learn more and more about each other as we keep playing each other and I think that's a good thing.
"They're the type of games we want to be involved in."
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