Coltman (25) will come off the bench in tonight's match against the Crusaders, in a season where he appears to have worked throw some throwing-in issues and is also getting round the field.
The Otago hooker appeared to have blown his chances of getting into the All Black picture last year, with some disappointing performances.
He was called into train with the All Blacks in 2013 but after a dip in form last year, the Alhambra-Union man had the cold shoulder from the national selectors.
Highlanders coach Joseph said Coltman had made strides over the off-season.
''I think both of our hookers and Sam [Anderson-Heather] when he gets a chance, have worked really hard in pre-season. Liam's game has improved immensely, all over the place and not just in his throwing. He is playing some really good footy at the moment,'' he said.
''Liam is a real show for the black jersey. I thought he was a real show for the black jersey last year but a couple of things happened and he did not nail a couple of performances when required. But every time he has had an opportunity for the Highlanders this year he has really nailed it.''
The back-up hooker job for the All Blacks, behind Dane Coles, is murky at best.
Keven Mealamu is not getting any younger and James Parsons is struggling to get starts.
Hurricanes hooker Motu Matu'u has been hot and cold while Chiefs hooker Hika Elliot has run into some disciplinary issues.
Meanwhile, statistics show Highlander Waisake Naholo is the form winger in the competition.
Opta Index stats show Naholo has played every minute for the Highlanders this season and is the side's top try scorer, crossing the whitewash on four occasions in six games.
Only three players have made more clean breaks in Super rugby than the winger (11), while his tally of 23 defenders beaten is also the joint-fourth best in the competition.
When it comes to gaining ground, Naholo is the Highlanders' go-to man, making more 476m, more than any other player in his team this year.
He has also proven himself to be a threat without the ball. His nine turnovers won are bettered only by one back and just five players in total this year.
