It is also a hurdle the 26-year-old has to overcome if he is going to play international cricket for England.
There was a time - perhaps before Australia's Adam Gilchrist helped redefine the role with his aggressive approach with the bat - when a stumping down leg side or a cracking catch was enough to justify your spot.
These days you have to add value with the bat as well.
It is something the Otago import is working hard at. But Cox also demonstrated just how valuable slick glove work can be during his Volts debut.
The fleet-footed Englishman pouched four catches - three of them up at the sticks - and assisted in two run outs.
His efforts helped Otago snatch victory against Wellington in a Super Smash match at the Basin Reserve late last month.
It was skilful display which Volts coach Rob Walter described as instrumental in helping turn the match. But Cox, while pleased with his work behind the stumps, was annoyed he was not able to offer more with the bat.
''We showed some serious bottle and nerve to get ourselves back into the game,'' he said.
''We won a game we had no right to win and ultimately that is the sign of a good side.
''But on a personal level I was not happy with my batting. It just didn't come off but I was over the moon with how I kept.''
He scored 13 not out from 14 deliveries but could not get the ball away to the boundary. A strike rate under 100 in the shortest format at the death just does not cut it, and Cox is determined to show people he is more than just a wonderful keeper who has been dubbed Mr Reliable by the Worcestershire faithful.
He debuted for the county when he was just 17 and still at Bromsgrove School. He scored 61, took four catches and stumped former England batsman Marcus Trescothick off Moeen Ali's bowling.
It was a dream start, but being thrust into the county scene at such a young age has had a negative impact on his record. His first-class batting average of 27.83 is the product of a young man trying to claw his way up to the level of those around him.
While he is considered one of the best keepers on the county circuit, he needs to score more runs to make the step up to international cricket.
He steered Worcestershire to its first T20 Blast title with an undefeated 46 in the final against Sussex last year. And he hopes a productive time in the Super Smash will enhance his improving reputation with the willow.
''It helps being over here. You look at someone like Sam Curran, who was over here last season and is now playing at the highest level.
''But people always talk about my wicketkeeping and my batting can quite easily get lost. But I do need to contribute more with the bat, particularly in four-day cricket.''
Cox was a very talented first five-eighth at school and played in a national under-18 trial - he shared the dressing room with England fly-half Owen Farrell. But shortly after he was offered a professional cricket contract and that was rugby done.
No regrets?
''None at all. We play sport to win trophies and to win the T20 Blast with Worcestershire was a highlight.
''I think I'll have a lot longer career in cricket than I would have in rugby. I've already had three operations.''
Shoulder twice. Hip once. And according to medical advice he should not be keeping.
''I got told my body was telling me no which is why I take great pride in my fitness now. I enjoy proving people wrong.''
He has already done that with the gloves. Remember when the Australian cricketers were ''taking the mickey'' out of the English keepers for fielding in front of the stumps instead of behind a few years back?
Well, turns out the English were right. Obviously, a direct hit is quicker, so Cox lets them go if he thinks they are going to hit.
But he did some testing with the England and Wales Cricket Board ''and we prove scientifically that it is quicker''.
It depends on your technique and it takes some mastering. But ''using momentum is quicker than standing behind and having to go back to the stumps''.
