Front row rising star Mullan is currently continuing his rehabilitation after shoulder surgery during the summer and concedes his selection as come as a welcome surprise.
The 22-year-old has now set his sights on the pre-season training camp for the England Senior Elite Player and Saxons squads in August to show his true international credentials.
"I was a bit surprised to get the call - but really pleased," said Mullan. "I didn't play in the game in England Saxons game in February when a frozen pitch called the game off and either of the summer tours so you wonder if you will be involved.
"Technically I'm also not back in full training and haven't played in three or four months so this has come as a real boost to me.
"I'm pleased to have kept my place and that they have kept faith with me. It's really competitive for places, David Flatman played really well for the England Saxons in the Churchill Cup and there are a number of really talented props pushing for spots.
"The call-up gives me a real training boost and a fresh incentive to target. The England squads come together in the second week of August so I have a four-week target to be involved in those sessions, I don't want to miss it."
Mullan was twice denied at England Saxons debut last season as a rearranged Guinness Premiership match prevented him from facing Portugal in January before a frozen pitch saw a last minute call-off of the clash with Ireland 'A' in February.
However, Mullan admits he must put any dreams of third time lucky to one side and purely concentrate on club rugby and getting back in action for Worcester Warriors.
"The squad will be looked at again at the start of next year when they review - so there are no guarantees for me getting a game yet," said Mullan.
"My priority has got to be to get fit and get out there for Worcester Warriors to show my form. Club rugby is all that is important to me and pulling the jersey back on after this time out in the Guinness Premiership.
"The injury is just one of those things, it will never go as quick as you would like and you have got to be patient to get it right," he added.
"You just want to rectify it and get back out there playing. I'm pleased with the progress so far and can't wait to get back into training again."
