Two episodes into its fourth season, “Grey’s Anatomy” continues to look a little peaked. Writing around Isaiah Washington’s departure got the season off to an understandably awkward start, and its roller-coaster of interlocking romances is definitely hurtling along a downward arc, from the latest dip in the Meredith-McDreamy misadventure to the credibility-straining Izzie-George-Callie triangle. So far, even a new batch of interns can’t correct the show’s course, which won’t prevent it from being a major hit but could hasten the rating dips experienced by other dramas (“Desperate Housewives,” anyone?), especially among more marginal viewers.

Fortunately, the show’s cast remains topnotch, milking the stronger moments for all they can. Those scenes, however, are coming at the kind of intermittent intervals that warrant a battery of tests, if not an emergency procedure.

Seeking to reclaim simpler days, the former interns at Seattle Grace now have the opportunity to torment the newcomers, with Cristina (Sandra Oh) going so far as to number hers, not bothering to learn their names.

The newbies, meanwhile, include Meredith’s half-sister (Chyler Leigh), though in typical “Grey’s” fashion, this triggers an existential crisis in Meredith (Ellen Pompeo) — as does her sort-of reconciliation with Dr. Shepherd (Patrick Dempsey), the once-and-former-and-once-and-oh-who-cares-anymore man of her dreams.

As for poor Callie (the consistently terrific Sara Ramirez), she’s being buffeted on two ends: Not only is she wrestling with having been named chief resident over the bitter Dr. Bailey (Chandra Wilson), but hubby George (T.R. Knight) is completing his improbable circuit of screwing every beautiful woman in the hospital with the equally messed-up Izzie (Katherine Heigl), proving again that when dramas begin running out of ideas, there’s no such thing as platonic friends.

The one pleasant wrinkle, thus far, has been a tentative rapprochement between McDreamy and his former friend Sloan (Eric Dane), with their “Brokeback” exchange providing one of the season premiere’s main highlights. On the down side, Diahann Carroll parachutes in again this week as Burke’s mother, dispensing Yoda-like advice to various characters that feels completely stilted.

“Grey’s” has built up enough good will that some viewers will follow its story lines wherever they lead, so there’s no reason for ABC to push the panic button. Still, with series creator Shonda Rhimes splitting her focus to establish the spinoff “Private Practice,” the show appears to be at a vulnerable stage unless the newer faces pop or the writing staff extricates itself from its unfortunate choices regarding the older ones.

In terms of whether the treatment requires major surgery or just popping a few Advil, let’s monitor the condition over the next few weeks.

Grey’s Anatomy

ABC, Thur. Oct. 4, 9 p.m.

  • Production: Filmed in Los Angeles by Shondaland and the Mark Gordon Co. in association with ABC Studios. Executive producers, Shonda Rhimes, Betsy Beers, Mark Gordon, Krista Vernoff, Rob Corn; co-executive producers, Joan Rater, Allan Heinberg, Tony Phelan; director, James Frawley; writer, Debora Cahn.
  • Crew: Camera, Herbert Davis; production design, Donald Lee Harris; editor, Sarah Boyd; music, Danny Lux; casting, Linda Lowy, John Brace. RUNNING TIME: 61 MIN.
  • Cast: Meredith Grey - Ellen Pompeo Derek Shepherd - Patrick Dempsey Cristina Yang - Sandra Oh Isobel “Izzie” Stevens - Katherine Heigl Alex Karev - Justin Chambers George O’Malley - T.R. Knight Miranda Bailey - Chandra Wilson Richard Webber - James Pickens Jr. Callie Torres - Sara Ramirez Mark Sloan - Eric Dane Lexie Grey - Chyler Leigh
  • Music By: