One year after “Grey’s Anatomy” defied conventional TV wisdom by blooming in April, no spring addition to the primetime sked looks like a game-changer.

In fact, pretty much all of midseason — at least since December’s bow of “Deal or No Deal” on NBC — has been underwhelming.

A whopping 27 series have preemed on the broadcast nets in 2006 and only one, CBS drama “The Unit,” is a lock to return next season.

This is in contrast to last year, when four skeins bowing post-January advanced to a second season, highlighted by megahit-in-the-making “Grey’s Anatomy.” Medical skein is one of the few April bows of the past decade to stick around.

Last year’s midseason crop also included hit crime dramas in CBS’ “Numbers” and NBC’s “Medium” as well as the Peacock’s “The Office,” which didn’t do much when it bowed but is on the rise this season.

In many cases this year, though, the quality simply wasn’t there for the midseason shows. A handful of skeins drew favorable reviews but none was an overwhelming consensus choice of critics.

There were mixed results for the shows that garnered the best reviews, with ABC’s “Sons & Daughters” and CBS’ “Love Monkey” doing little while the well-reviewed CBS combo of “The Unit” and “The New Adventures of Old Christine” have fared better.

“The Unit,” which bowed in mid-March, has averaged a 4.4 rating in adults 18-49 and a 6.2 in adults 25-54 for its first eight episodes. It also should be the season’s most-watched newbie at about 16 million viewers.

Verdict is still out on “Old Christine,” which started hot (holding about 95% of its “Two and a Half Men” lead-in) before settling into the 80%-82% range — on par with “Out of Practice” in the slot last fall.

Another midseasoner to make some noise was ABC’s “American Inventor,” although this poorly reviewed series slipped to a 3.3 average for its previous three segs after earning a 4.7 for its first three outings.

Critics also hurled bricks at Fox’s “Unanimous,” which will end the season as the No. 1 new program in 18-49 (roughly 6.0) by virtue of retaining about half of its “American Idol” lead-in on Wednesday.

Both “Inventor” and “Unanimous” could return in some form next season.

Auds mostly yawned at the midseason comedies, including NBC’s “Four Kings” and “Teachers,” Fox’s “The Loop” and “Free Ride,” ABC’s “Crumbs” and CBS’ “Courting Alex.” They also gave up quickly on two NBC dramas that opened decently, “Book of Daniel” and “Heist,” and have offered only modest support for the net’s “Conviction.”

And then there were the real turkeys of the new year — ABC comedy “Emily’s Reasons Why Not” and NBC unscripted skein “Celebrity Cooking Showdown” — which wasted massive promotional efforts by their respective nets and were cooked after one airing.

It’s also been brutal for new shows on the WB and UPN. Latter struck out with “South Beach” and “Get This Party Started,” while all four of the Frog’s new shows have failed.

Nobody expected much from comedy “Modern Men,” drama “The Bedford Diaries” or reality entry “Survival of the Richest,” but dramedy “Pepper Dennis” has been a disappointment. The Rebecca Romijn starrer averages a 1.1 rating compared to a 2.0 for lead-in “Gilmore Girls” (2.0).

Along with the WB and NBC, ABC has had a weak midseason. The return of “Dancing With the Stars” was a nice addition to the sked, but dramas “In Justice” and “The Evidence” proved to be Nielsen lightweights.

If the Alphabet is edged out by Fox for the season’s demo crown, it can look back at the lackluster return it got from its midseason offerings.