While the Rangers remain on the lookout for options that may improve the depth of their 2013 starting rotation, it appears the core of the rotation will all be locked up through at least 2017.

Two sources acknowledged Wednesday the club is very close to a contract extension with left-hander Matt Harrison. The only obstacle before an announcement may be the results from a physical exam. The announcement could come before the end of the week.

"We're still talking," Harrison said at Rangers FanFest last weekend. "We're excited about the possibility of a long-term deal, but we still have thinking and talking to do."

The deal is expected to be a five-year deal worth in excess of $50 million. Harrison, 27, is in his second year of arbitration eligibility and is scheduled to exchange arbitration figures with the team on Friday. The deal would buy out three years' worth of free agency.

In addition, the Rangers were one of four teams represented at right-hander Javier Vazquez's five shutout innings of work in a Puerto Rico winter league playoff game. Vazquez, 36, is weighing a return to the majors after sitting out 2011. The Rangers also maintain contact with agent Scott Boras about right-hander Kyle Lohse.