Poulter defeated Senden on the opening day of group games, and as he sat out the morning action, he knew he would be through if his fellow Hertfordshire golfer got at least a half.
The 21 year old, who led The Open Championship as an amateur last summer and then won the Portugal Masters in only his third start as a professional, did better than that, but had to go to the final green.
Winning the third, fourth and sixth took him three holes ahead, but Senden threatened to turn things round when he birdied the 13th and 14th to level.
A poor chip cost him the next, Lewis made an 18 footer for birdie on the 16th, but three-putted the short 17th to be only one up again.
A half in par fives at the last, though, set up a clash between him and Poulter to decide who topped the group.
