``He's gone up about three chest sizes,'' said Birkenshaw excitedly. ``He used to be a loose 42 and he's come back a tight 46.''
While some cricketers were earning themselves club fines and extra training for putting on weight during the close season, this expansion in Mullally's lean and lanky 6ft 5ins frame was greeted by Birkenshaw not as a sign of sloth and gluttony but as impressive evidence of a winter's graft and dedication to improved fitness, strength and stamina.
The further proof required to put Mullally back into contention for an England place was there in an extra yard of pace and a new ability to swing the ball into the right-handers almost at will; attributes which will surely underwrite his return to the Test side this week. ``He's ready,'' insists Birkenshaw. ``He's a much better bowler now than when he was first picked for England in 1996. He was at a crossroads last season when he had injury problems and got frustrated, but you only had to look at him when we reported for pre-season training to know that he'd taken the right direction.
``Because he's worked so much on his fitness, he's now got the confidence to be harder in his attitude to batsmen, and it's paying off with the best bowling of his career.''
Prior to Leicestershire's current championship game against Lancashire the statistical support for that view amounted to 41 first-class wickets at 18.14 apiece and, if that alone was not enough to sway the England's selectors to pick him at Headingley on Thursday, the fresh memory of career-best NatWest Trophy figures of five for 18 in the total eclipse of Warwickshire last week was surely what did the trick.
It was a performance both brilliant and timely, demonstrating for any remaining doubters that Mullally is indeed now in full possession of the left-arm seamer's greatest weapon, the ability not only to slant the ball away from right-handed batsmen but also to swing it back through their defences.
``The whole thing is working so much better than before,'' says Mullally. ``I had a knee operation in September and to give myself a chance to recover properly I had a complete break from cricket for the first time in 10 years and instead put in a lot of work in the gym back home in Australia.
``I spent stacks of time on weights, building upper-body strength, and since I can now generate good pace off a shorter run I've got the control to get closer to the stumps and claim my share of lbw decisions.''
Mullally, who has played in nine Tests and eight limited-overs internationals, was a surprise omission when England's selectors last week named a squad of 37 players for next summer's World Cup, but unlike team-mate Chris Lewis did not vent his disappointment in public.
``One step at a time,'' he sensibly observed. ``The first was to get back into the Test squad, which happened at Trent Bridge. The next is to get back into the side and then to be on the plane for the tour of Australia next winter. After that things will take care of themselves, if I'm doing the business.''
If he ``does the business'' at Headingley this week, the next size 46 blazer he's measured for will have a crown and three lions on the chest instead of a running fox.