A spot has opened for odds favorite Rachel Alexandra to run in the 134th running of the Preakness Stakes, ironically thanks to the owner of Triple Crown contender Mine That Bird.

Mine That Bird owner Mark Allen said Monday he wouldn’t enter colt Indy Express into the second jewel of the Triple Crown. That clears the way for the Kentucky Oaks winner to enter the field of 14 for Saturday’s race at Pimlico.

Allen had considered entering Indy Express — winless in nine career starts — over the weekend to take a spot from Rachel Alexandra, but he reconsidered after talking to Mine That Bird trainer Bennie Woolley Jr. and co-owner Leonard Blach.

The race is limited to 14 starters, with preference given to those already pre-nominated to the Triple Crown.

Good for Allen. He would have been vilified had he entered a winless Indy Express just so that Rachel Alexandra (Mine That Bird’s chief competition) couldn’t run in the Preakness.

Rachel Alexandra has been flawless so far in 2009, winning seven of her last nine races. She would add a little excitement to the Preakness, especially after Mine That Bird won the Kentucky Derby two weeks ago despite being a 50/1 long shot.