The 14th Texas cavalry regiment left Texas in 1862, as part of Johnson's brigade along with the 15th, 16th and 17th Texas regiments. This brigade was enroute to join Van Dorn's army at Corinth, Ms.
As you now know, the 14th was the only regiment of this brigade to actually reach Van Dorn. The others were retained in Arkansas, and most were subsequently captured at Arkansas Post in January, 1863.
Enough of the soldiers of the various regiments at Arkansas Post escaped capture to form what became known as the 17th Texas consolidated dismounted cavalry regiment.
This regiment fought at the battle of Mansfield.
Now, this is only conjecture, but perhaps your man was serving with this consolidated regiment formed of men from various other regiments that had a previous connection to the 14th Cavalry regiment.
However, I did not find Conner in the roster for the 17th Texas consolidated regiment at http://www.itd.nps.gov/cwss/index.html
And, a search for Conner at this same web site does not show him on the roster of any other regiment than the 14th Texas cavalry. Of course, this roster information is not infallible.
Wish I could be more helpful.