I found the quote from a book I was reading which made me ask this question: "In view of his precarious position in Greece, where he had few possessions and many enemies (including a resurgent Sparta)..." ('Diving the Spoils, the War for Alexander the Great's Empire' by Robin Waterfield', page 210, line 3).

Yes, if they would be willing to commit to radical social reform.

Once they lost their empire and unequal allies, they were reduced to the status of "just another city-state". However, they controlled all of Lakonia, which meant they were still one of the richest states in mainland Greece. According to Aristotle, their land had the potential to support an army of 1,500 cavalry and 30,000 hoplites. Unfortunately, massive wealth accumulation in the hands of a smaller and smaller body of citizens meant that very little of this potential could actually be brought to bear.

For decades after Leuktra, Sparta tried to regain supremacy in the Peloponnese and to recover Messene. They failed because there were simply too few enfranchised citizens to fill out the ranks of the army; those who did not make the income requirement to gain citizen rights understandably didn't feel terribly committed to the Spartan cause.

Sparta was briefly resurgent in the late 330s BC, but the Macedonians soon smashed their rebellion, and the city-state was mostly passive for a century (as far as we can tell). Then came the reforms of Agis and Kleomenes. These kings actually redistributed the land, so that Sparta went from having 100 citizens to having 9,000. This gave them another day in the sun and a couple of notable victories before the Macedonians came down again and crushed them at Sellasia in 222 BC. King Kleomenes fled and died in Egypt. Sparta was never relevant again after that.