Next up is a long two-round finale.
Walker and Nitties shot 5-under 67s on Saturday for a share of the lead at 7 under with Brett Wetterich (68) and Matt Jones (71) at TPC San Antonio, where the Oaks Course soaked up a drenching that will make for a 36-hole finish Sunday.
Muck and mud squished under the morning gallery after more than 3 inches of rain washed out play Friday. But fairways drained and greens stayed firm, drawing praise from some in a field that has grumbled about the new Greg Norman-designed layout.
"The greens are what they are," said Wetterich, who birdied his final three holes. "You're going to gripe about it, I think that's more advantage for other people that aren't and just kind of go with the flow."
Tour rookie Garth Mulroy (67) was a stroke back along with Charley Hoffman (70), James Driscoll (68), J.B. Holmes (70), Pat Perez (66), Tim Petrovic (68) and Aron Price (68). Ernie Els, a two-time winner this year, was two shots back at 5 under after a 67.
"Hoping for Texas winds tomorrow," Els said. "It's going to be a long day but I'll be up for it."
PGA Tour officials hadn't ruled out stretching the tournament into Monday if storms delayed the tournament again. The National Weather Service called for a 40 percent chance of rain Sunday.
Walker, who missed the cut in three of his last four tournaments since April, grabbed a share of the lead on a course he knows better than most.
The San Antonio resident played TPC San Antonio -- where the Texas Open moved this spring after 15 years at La Cantera Golf Club -- before most anyone last winter. That familiarity started paying off.
After starting the round four back, Walker birdied three holes on the front nine and another three on the back leg. He used a sand wedge to put a 111-yard approach about seven feet from the cup on the par-4 11th, then sank the putt for birdie.
"I've gotten way behind and it's hard to claw your way back from the back of the pack," Walker said. "I've been doing it but it's not fun. It's nice to get out and make the cut, you know, fairly easy."
Els also began a push. The current money and FedEx Cup points leader, who also is the only player in the field ranked in the top 10, missed the cut last week at The Players Championship while working through a bad swing.
Els arrived in Texas focused on releasing his club earlier and not being so "handsy through the hitting area." Though still feeling conservative with his drivers, Els was on target with his driver.
On the par-5 second, Els got out of a fairway bunker with a 5-iron before sinking a 17-footer for one of his five birdies. He hit par on every other hole.
"I felt one more tournament could really do it for me, and although it didn't happen in the first round, I feel it's really coming around now," Els said.
Vijay Singh, who played with Els and is arguably the other biggest name in the tournament, shot for par in the second round and made the cut at 1 over. Sergio Garcia shot a 68 and was four strokes back.
Zach Johnson, the two-time defending tournament champion, couldn't erase the damage from his disastrous opening-round 80. He missed the cut at 4 over.
Johnson beat Driscoll in a sudden-death playoff at this tournament a year ago, and Driscoll on Saturday blew his chance for a five-way tie for first with a bogey on his final hole. His approach missed the green on the par-4 ninth, and his 8-foot putt for par missed by 2 feet.
No. 9 also cost Jones sole possession of the lead.
Jones, who led after the opening round, birdied on the par-5 eighth to reach 8 under with one hole to go. But he drove his drive on No. 9 into the tall grass and rocks to the right of fairway, and couldn't recover to make par.
Scott Piercy began the round 3 over but birdied six holes on the front nine and shot a 64 for the day's best round. The 31-year-old was four shots back.