In the absence of major works of art coming on the market through restitution, the forthcoming evening sales in New York at Christie’s and Sotheby’s in May promise to be less dominated by individual star works and more reflective of general trends in the market than last fall’s auctions. The one exception will be Rothko’s “White Center (Yellow, Pink and Lavender on Rose),” which David Rockefeller has consigned to Sotheby’s in exchange for a guarantee that is rumored to be $46 million, which is more than twice the artist’s previous auction record.

“When you put an estimate on something that is truly a masterpiece, you have to think somewhat out of the box,” a senior specialist in contemporary art at Sotheby’s, Anthony Grant, said. “You cannot just extrapolate from previous prices that have been established.”

But the co-head of postwar and contemporary art at Sotheby’s rival, Christie’s, Amy Cappellazzo, said that although Rockefeller is “one of those magical names in terms of provenance,” she had no regrets about passing on a deal with those terms. “You have to figure out: At what point does a deal continue to make sense, and at one point is it risky?” she said. “Maybe I’d rather do five deals at $10 million each, because I’d still be tapping a deeper price point in the market, [but] I would be distributing my risk accordingly.”

The leading lot in Christie’s postwar and contemporary sale is Warhol’s “Lemon Marilyn,” which is estimated to bring more than $15 million. But Ms. Cappellazzo said she still has a few balls in the air. “There are a couple of things hanging out there,” she said. Both houses said it was too soon to put high-low estimates on their evening sales.

Neither house has any works estimated at more than $18 million in its Impressionist and Modern sale. The leading lots in Sotheby’s sale are a Cézanne watercolor, “Nature Morte au Melon Vert,” being sold by the Asian art dealer Giuseppe Eskenazi, and a Rose Period Picasso, “Tête d’Arlequin,” both estimated at between $14 million and $18 million.

At Christie’s, the top lots include a Juan Gris, “Le pot de geranium,” estimated at between $14 million and $18 million; a Modigliani, “Madame Menier,” estimated at between $12 million and $16 million, and a Kirchner, “Dodo mit Großem Fächer,” estimated at between $12 million and $18 million.

The co-chairman of Impressionist and modern art at Sotheby’s, David Norman, described the Picasso as “one of the most emotional and poetic and resonant works we’ve had by him.” It depicts a young boy, most likely a street urchin from Montmartre, whom Picasso painted several times.

Mr. Norman described the painting as weighted with a sense of Picasso’s self-identification, both with the anonymous boy and with the image of the harlequin, which would be an important motif throughout his career. “A lot of artists at the time saw these soulful, itinerant, poor performers on the margins of society as a metaphor for how they felt about themselves.”

Sotheby’s also has a late Picasso, “Femme Nue Assise,” from 1965, estimated at between $8 million and $10 million. Late Picassos have appreciated enormously in recent years. Because they are “expressionist and aggressive,” Mr. Norman said, they fit well in the collections of people who buy mostly contemporary art. “People with Bacons and Basquiats now feel its sort of essential to have a post-1960 Picasso,” he said.

As to whether the Rockefeller Rothko can draw its guarantee or higher, Mr. Grant said he was confident there are buyers interested in the painting in that price range. “Whenever we put an estimate on a work of art and make a financial commitment, we play this exercise where we actually write down who will buy this painting,” he said. “If you come up with no names, you have a problem. If you come up with three or four names, you have an estimate.”