Pozzi finished sixth in the 110m hurdles, with Jamaican duo Ronald Levy and Hansle Parchment taking gold and silver respectively and Australia's Nicholas Hough third.
He accepted he "wasn't good enough" after hitting the first hurdle.
England have won only two medals from the opening three days of athletics action.
Pozzi, 25, won gold in the 60m hurdles at the World Indoor Championships in March, but this performance was nowhere near as slick as the final in Birmingham as he registered a time of 13.53.
And he admits he never recovered his momentum as the Jamaican pair went away from him and his technique faltered under the pressure.
"I was trying to play catch up but I rushed it," he told BBC Sport.
"I started to make some headway but through rushing things made mistakes and it just wasn't good.
"There were several people who did a better job and they got what they deserved."
With Jamaica's world and Olympic champion Omar McLeod opting to miss the Games, Pozzi knows there are more testing fields to overcome if he wants to claim major medals.
For Levy it underlined his claims to being the main threat to McLeod's dominance.
The 25-year-old was the only man to beat his compatriot in 2017 with a break-out win at the Diamond League event in Paris.