During this week’s sales of Contemporary and Post-War art, Sotheby’s and Christie’s will have head-to-head matchups of work by Jeff Koons, Jean-Michel Basquiat, and Mark Rothko. The battle between auction house rivals has been fairly lopsided in the Contemporary market for the last few seasons.

It’s been three years since Sotheby’s has been able to match or beat its rival’s sales totals. But this season, with all eyes fixed on Sotheby’s as never before, the house comes out swinging with two major Francis Bacon canvases, a self-portrait and “Second Version of Study for Bullfight No. 1.” Christie’s counters with three key works: Andy Warhol’s “Liz,” estimated at between $25 million and $35 million; Gerhard Richter’s “Dusenjager,” estimated at between $10 million and $15 million; and Lucian Freud’s “Ib and Her Husband,” (estimate upon request).

Next come the artist-for-artist battles. Each house has a monumental Jeff Koons sculpture from his celebration series. Sotheby’s has “Hanging Heart,” estimated at between $15 million and $20 million; Christie’s has “Diamond (blue),” (estimate upon request). Both works are mammoth — too big to be displayed in anything less than a lobby.

Both houses have black-and-gray Rothkos. Sotheby’s untitled picture is estimated at between $12 million and $18 million, while Christie’s is selling one estimated at between $10 million and $15 million. Each house has additional Rothkos. Sotheby’s has a smaller, untitled canvas that is blue-onblue and estimated at between $3.5 million and $4.5 million. Christie’s has two more major works in “Untitled (Red, Blue, Orange),” estimated at between $25 million and $30 million, and “No. 7 (Dark Over Light),” estimated at between $20 million and $30 million, and a minor work, “Green, Blue, Green on Blue,” estimated at between $3 million and $5 million.

Last month’s poor showing in London for paintings by Basquiat hasn’t dented the ambitions of his collectors. These sales have four good Basquiats seeking the higher valuations established with this spring’s sales of work for $14 million and $10 million. Christie’s has

“Sugar Ray Robinson,” estimated at between $6 million and $8 million, and”Untitled (Black Figure),” estimated at between $8 million and $12 million. Both are from 1982, the highly prized early year in the painter’s career. Sotheby’s has works from 1981 in “Untitled,” estimated at between $7 million and $9 million, and “Untitled (Electric Chair),” estimated at between $8 and $10 million.

According to author of the Baer Faxt newsletter, Josh Baer, there are collectors willing to pay $30 million or more for the right Basquiat. But he quickly adds, “not the ones in auction, but private ones.” These four sales could be a crux moment in the Basquiat market.

With so many big-ticket pictures on offer, it would be easy to miss the many gems in these sales. Christie’s has Ed Ruscha’s “Burning Gas Station,” estimated at between $4 million and $6 million. This pristine work from Ruscha’s rare but iconic series of gas station pictures should set a world record for the artist.

An early, untitled work by Robert Ryman, estimated at between $8 million and $12 million, also has a chance to set a new world record for the artist. The large painting from 1966 is composed of broad, horizontal white stripes.

Christie’s is selling a Richard Prince, “Piney Woods Nurse,” estimated at between $1.8 million and $2.2 million. (Phillips de Pury ahas “Registered Nurse,” estimated at between $1.5 million and $2.5 million.) There are great paintings by Lee Krasner and Joan Mitchell in the house’s evening sale and an almost overwhelming Morris Louis in the day sale. Sotheby’s, also, has two great Morris Louis canvases. The artist’s prices have been climbing rapidly and there is a traveling show of his work currently at the Hirschorn in Washington, D.C.

Other highlights of the Sotheby’s sale are: a Cy Twombly, “Untitled,” estimated at between $5 million and $6 million; a “Self-Portrait (Green Camouflage),” estimated at between $9 million and $12 million, and Warhol’s “Four Jackies,” estimated at between $4 million and $6 million. Warhol’s Jackies have been selling very well in London in June and October. It’s a series that seems to have gained traction in the market.