Owen gave his England team-mates Defoe and Peter Crouch a lesson in finishing at Fratton Park, taking his 52nd-minute goal clinically before Obafemi Martins and Danny Guthrie wrapped up the rout late on.
In contrast, Defoe missed a host of chances and grew increasingly frustrated as he was well shackled by the impressive Sebastien Bassong.
Adams backed his own misfiring striker however, saying it was just not Pompey's day.
"Michael has done that all his career," he said.
"You switch off for two minutes and he can punish you. But I've got one of those as well. And I wouldn't swap Jermain for Michael.
"The first goal was very important today. I didn't think it was our day. We made mistakes and gave them the goals and you don't win games if you make mistakes.
"The result was very disappointing. It was a very bitty game.
"But credit to them as well. They have come to do a job and they have done it very well. They were difficult to break down even though we had our chances."