He held the lowest score of the day until Tom Watson shot a 65.
The 38-year-old Australian took Jeev Milkha Singhs spot in the field of 156 on Tuesday when the Indian player pulled out with a rib injury. Senden took full advantage of the near windless conditions to make four birdies in five holes on the back nine.
I played solid, Senden said. A couple of good saves, and holed a couple of good putts on 13 and 14.
Senden holed birdie putts from 30, 20 and eight feet from the 13th to 15th holes, and got out of a bunker to sink one from 35 feet at the 17th.
Senden said he was still the fourth reserve for the British Open when he missed the cut at the rain-disrupted John Deere Classic on Saturday in Silvis, Ill.
There was not a lot of hope for me but, when I arrived in Dallas, I found out in the morning that I was the first reserve. Thats a good chance for me, Senden said. I decided to take the chance and travel overnight and get here Tuesday morning.
When I arrived at the airport I got a text message from my caddie and he said that Jeev Milkha Singh was not feeling too great with his ribs and that he was pulling out of the event. So I was lucky enough to be in the field.
Senden, who won his only PGA title at the 2006 John Deere Classic, tied for fourth at the 2007 PGA Championship for his best finish at a major.