Orient booked next month’s trip to League Two club Salford with a hard-fought 1-0 away win on Tamworth’s artificial pitch.
Wellens said the playing surface made Monday’s first-round tie extremely difficult.
“We trained on astroturf three or four days ago. It was nothing like this. This is, like, really rubbery. A million per cent, the players will wake up with bits of rubber in their beds and around the house,” he continued.
“History tells us – Huddersfield came here and got beat last year when they were in a great vein of form. And Tottenham came here and found it very difficult.
“Its a difficult place to come. Its difficult to dribble, its difficult to move the ball properly. To come out of here injury-free is a bonus.”
The victory made it five in six matches in all competitions for the O’s, and Wellens hailed the character shown by his team.
He said: “I thought we had more or less complete control. I’m really pleased with our goalkeeper and back four. They defended really well, to come here and get a clean sheet.”
Forward Alfie Lloyd, on loan from Queens Park Rangers, was sent on as a substitute in stoppage time and almost got the O’s a second goal.
And Wellens is delighted with his attacking options as they head into 10 league and cup matches between now and the New Year.
“We brought Alfie on because of putting ball in the box. He gives you that extra height, and obviously he’s fresh, and got us up the pitch really well,” he added.
“I’m pleased with the front players, the options (are) all fully fit. Alfie looks like a different dimension to the others. He’s robust, he’s big, he’s strong, he’ll run in behind. I’m happy with him.”