The Baggies made nine changes to take on the Tractor Boys at Portman Road but the plan didn't work as they were eliminated by a 69th minute Grant Leadbitter penalty which allowed Ipswich to record a 1-0 victory.
But Newton said it wasn't the player changes, but rather the fact some players simply did not perform on the night that contributed to the defeat.
"We have been doing that since the beginning of the competition, and kept faith in those players, so there are no regrets in the changes," he said.
"But you don't need to be an expert to know it was a poor performance, individually and collectively, from the start to the end.
"We did not show enough desire and paid the price.
"However, (debutant) James Hurst was fantastic on his debut in a side which did not perform well.
"We just cannot carry that amount of poor performances. Some games you just cannot put your finger on it, too many players did not turn up tonight. It is bewildering."