rey’s Anatomy” has lost a lot of its luster.

Terrible storylines, the departure of Isaiah Washington and on-set tension with Katherine Heigl have all been factors.

Season 3 was a downer that featured storyline winners such as the end of Burke and Cristina, the insipidly boring Jane Doe plot with Karev, Meredith trying to commit suicide and the beginning of the worst TV couple ever created in George and Izzie.

Season 4 had such lowlights as Izzie saving a deer, contrived Meredith-Derek drama with the Rose subplot and Cristina acting like a sad and pathetic human being for the entire season.

About the only positive things that happened were the end of George and Izzie’s relationship and Meredith and Derek getting back together forever, as promised by Shonda Rhimes.

An embarrassing promo that aired on ABC with Rose telling Derek she was carrying his baby forced Rhimes to announce that Rose would be gone shortly and that she did not lie to her fans.

One of the main problems with the last couple of seasons is that the show lost its sense of humor.

Rhimes’ answer to this involves injecting new blood into Seattle Grace this season. Kevin McKidd joins the show tonight in the role of a doctor who takes an interest in Cristina.

Rumor has it that he has won over show producers and will be sticking around as a regular character.

It will be fun to watch Cristina get involved in a relationship again, as she was too depressing last season.

Another new character will be a brain surgeon played by Brandon Scott who is being brought in to work with Derek.

The key to the season will be the writing. If Rhimes can create interesting arcs with good payoffs and the characters are allowed to have fun again, “Grey’s Anatomy” can become an Emmy-nominated drama once more.

Season 5 starts tonight at 9 p.m. on ABC.