Peyton Manning is "not likely" to start against the Texans in the opening game in Houston.

The Colts say doctors have decided that Manning should not practice. New diagnostic tests were initiated after he "experienced soreness in his back" over the weekend. The team--in its first open response to the eruption of the new neck surgery rumor--says the soreness "was originally thought to be a normal reaction to his rehabilitation regimen."

But now it's not clear what it might be. The Colts are drawing no conclusions, saying it "serves no useful purpose to speculate about hypothetical outcomes."

"When and if there are concrete medical facts to report we will do so," says the team's prepared statement which was emailed to media outlets late this morning.

Text of the Colts statement:

In response to a number of media inquiries, the Colts issue the following update on Peyton Manning’s status.

During the last week, the rate of improvement in Peyton’s rehabilitation process slowed. Over the weekend Peyton experienced soreness in his back. It was originally thought to be a normal reaction to his rehabilitation regimen. When the soreness persisted, the Colts medical team decided to initiate diagnostic tests and to consult with a number of specialists around the country who have been involved in Peyton’s case from the outset. That process continues. As a result of the most recent development the doctors have decided that Peyton will not practice. His participation therefore, in Sunday’s game versus Houston will likely be doubtful. We will update his playing status as required by NFL policy as the week goes on.

At the conclusion of the diagnostic process, if there are any new developments in the prognosis which we outlined for Peyton at the start of training camp we will report them. As of now Peyton continues to deal with a complicated neurological recovery, the end date of which is unpredictable.

As was stated at the outset, it serves no useful purpose to speculate about hypothetical outcomes. When and if there are concrete medical facts to report we will do so.

We appreciate your consideration in this matter.