Ian Poulter trails Kevin Na at Crowne Plaza Invitational

Poulter has switched back to an old putting grip for the tournament in Texas

Ian Poulter wants to answer criticism from peers as he sits two shots off the lead at the Crowne Plaza Invitational.

The Englishman, 39, produced a three-under-par 67 to move to eight under at the halfway stage at Colonial, enough for second behind American Kevin Na.

Rickie Fowler and Poulter were recently voted the most overrated players by PGA Tour professionals, five days before Fowler won the Players Championship.

"He's taken care of business, it's time to take care of mine," said Poulter.

Poulter - who described results of the anonymous players' survey as "water off a duck's back" - has never won a strokeplay event in the United States but backed up a 65 on Thursday by carding six birdies and three bogeys in wet conditions.

He has changed back to an old putting grip for the tournament in Texas after looking at old photographs, and sits first in the field for strokes saved on the greens.

"The nice thing is I've been searching for something for several months," said Poulter, who is without a win since 2012. "This might be the thing that gets my putting back on track."

Kevin Na only carded one bogey on Friday to take the outright lead

Na, 31, has not won a tournament since October 2011 and picked up five birdies on Friday before ending his round with a bogey on 18.

American Boo Weekley is third, a shot behind Poulter, while Masters champion Jordan Spieth slipped from being co-leader after round one to seven shots off the pace with a three-over-par 73.

Scotland's Martin Laird is level with Spieth on three under, with compatriot Russell Knox at two under.