And though it's still early in the game, the consensus is sublease will rise through year's end. "It's hard to predict how high it will go, but I know it will go higher," Matthew Heidelbaugh, senior director for Cushman & Wakefield of Texas Inc., tells GlobeSt.com.

C&W's latest count shows 4.18 million sf of sublease space, of which 2.48 million sf are empty and 1.7 million sf are occupied while being marketed. One year ago, C&W's researchers had logged 3.3 million sf of sublease space at the Q2 close.

Grubb & Ellis Co.'s researchers found 4.02 million sf of sublease space at this year's Q2 close versus 4.19 million sf at the end of Q1. The change is attributed to sublease rolling to direct space and not a sudden spurt of leasing in a market with 177.5 million sf overall. The Dallas trend is in line with Grubb & Ellis' chief economist Robert Bach's assessment.