PALM HARBOR, March 17, 2014 (AFP) - The 42-year-old from Brisbane sank a 68-foot chip shot to birdie the 16th and a 22-foot birdie putt at 17 on his way to claiming the $1.02 million (733,600 euros) top prize at the $5.7 million (4.09 million euros) event.
"I'm just so happy to come out on top," Senden said. "I just went out there and felt comfortable throughout the first 10 or 12 holes.
"Then I started to make a few little errors and get a little uptight on the back nine, but made some really nice saves and putts coming down the stretch."
Since his lone prior US PGA win at the 2006 John Deere Classic, Senden had played 205 events with four runner-up efforts his best showings.
Senden fired a one-under par 70 in the final round to finish 72 holes at the Copperhead Course at Innisbrook on seven-under par 271, defeating American Kevin Na by one stroke.
"With the difficulty of the course, the winning score always stays in single figures so I knew if I could just stay in the moment I could just give it a shake," Senden said.
Senden, who was second at this event in 2007 and 2008, booked a berth in next month's Masters and became the first over-40 winner on the US PGA Tour since American Woody Austin last July.
Clinging to a share of the lead, Senden sank his pitch from the rough at the par-4 16th to seize the top spot, dropping the wedge shot short and watching the ball roll into the cup.
"It was just like a magic shot," Senden said.
On 17, he followed with the long birdie putt to grab a two-stroke edge and parred the last to set the mark to beat.
"At 17 I had the line and struck in well and it went right in the middle," Senden said.
Na sank a 14-foot birdie putt at 17 to give himself a chance to force a playoff with a 40-foot birdie attempt at the last but missed, settling for his best US tour finish since 2011 at Las Vegas.
"I made two great birdies coming in, but it wasn't good enough," Na said. "I'm really pleased with how I played. I just got outplayed the last few holes."
American Scott Langley was third on 279, one stroke in front of England's Luke Donald and Americans Will MacKenzie and Robert Garrigus.
Garrigus, who led when the day began, stumbled with double bogeys at the third and sixth and a bogey at the fourth to fall back, opening the door to a fistful of rivals.
Senden had a tap-in birdie at the par-5 opening hole and sank a three-foot birdie putt at the fifth to take sole possession of the lead at eight-under.
Na sank a 10-foot birdie putt at the fifth to match him for the lead briefly but followed with back-to-back bogeys and a double bogey on the next three holes to fall back.
Senden found a greenside bunker at seven and stumbled to his first bogey in 31 holes to stand on seven-under, but when nearest pursuer Langley took a bogey at 12, the Aussie found himself two strokes clear of the field.
Senden hit a bunker at the 12th and missed an 11-foot par putt to slide back to six-under and Langley answered with a five-foot birdie at 14 to match him for the lead.
When Senden lipped out on an eight-foot par putt at the par-3 13th and took a bogey, Langley was alone at the top.
But Senden responded with a 15-foot birdie putt at the par-5 14th and moments later, Langley missed a 10-foot par putt at 16 to leave the Queenslander back in front by himself.
But momentum swung again when Senden found a bunker at the par-3 15th and made bogey, setting up the final drama.
Leading scores after Sunday's final round of the $5.7 million US PGA Valspar Championship (par 71, USA unless noted):
277 - John Senden (AUS) 72-71-64-70
278 - Kevin Na 70-68-68-72
279 - Scott Langley 71-69-69-70
280 - Will MacKenzie 73-70-68-69, Luke Donald (ENG) 71-72-67-70, Robert Garrigus 69-66-70-75
281 - George McNeill 73-71-67-70
282 - Graham DeLaet (CAN) 75-68-71-68, Gary Woodland 72-71-70-69, Matt Every 68-71-72-71, David Hearn (CAN) 71-70-70-71, Matteo Manassero (ITA)69-70-71-72, Justin Rose (ENG) 71-68-69-74
283 - Bae Sang-Moon (KOR) 72-73-71-67, Charles Howell 71-70-74-68, Bill Haas 69-73-72-69, Jason Dufner 72-73-68-70, Chesson Hadley 75-70-67-71, Jason Kokrak 74-68-68-73
284 - Carl Pettersson (SWE) 71-70-71-72, Jordan Spieth 71-70-71-72, Jim Furyk 71-69-71-73, Freddie Jacobson (SWE) 70-71-70-73, Ted Potter 73-71-67-73
285 - Ryo Ishikawa (JPN) 73-72-72-68, Cameron Tringale 74-71-70-70, Brian Harman 71-70-73-71, Morgan Hoffmann 74-69-71-71, Josh Teater 73-70-70-72, Russell Knox 70-73-70-72, Charley Hoffman 70-72-67-76