While the first team secured a last-gasp win over Newcastle Falcons, the Academy duo were on the field as England scored in the ninth minute of injury-time to deny Wales as the U21 Six Nations came to a close.
Mullan started at hooker for A clash that was watched by a crowd of over 3,500 and Cox climbed off the bench to play his part in the dying minutes. Warriors wing Miles Benjamin was forced to withdraw from squad through illness.
England won two, lost two and drew one of their five Championship matches. And coach Nigel Redman said: "The score was probably a fair result although that was a game we probably could have won.
"In the last 10 minutes they showed the tempo and the intensity that we have been asking for and coaching and when their backs were against the wall they showed what they could do."
There was also success for a trio of Warriors over Italy as England U18s continued the countdown to this season's AER European Championships with an impressive 29-15 victory over Italy U18s.
Worcester youngsters Michael Penn, Harry Owens and Joel Diggin all featured as England overcame a big Italian pack and energy-sapping heat in Mantova.
Full-back Penn capped a fine individual display with a second half try from a flowing move.
The fixture was England's second of three warm-up games before they play Portugal in their opening AER game in Biarritz on April 1.
"We are absolutely delighted with the way we played today," said England manager Ted Atkinson. "We still have a bit to do in one or two areas but the side again showed that they have a bit of dog in them.
"Italy had a big set of forwards and it was a very hot day so the conditions were energy-sapping, but the boys stood up very well."