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The left-armer is in a head-to-head battle with Wellington's Mark Gillespie to nab the final spot in the Black Caps test squad which is being kept vacant for a pace bowler.
Otago all-rounder Jimmy Neesham may have forced a change to those plans with a fine performance of four for 65.
But Wagner has Ian Bell's vote. The England No 5 posted an undefeated 127 on the opening day of the four-day game to help England reach 357 for seven.
''I think Wagner ran in all day and was quite impressive, actually,'' Bell said.
''[He has] Good pace and he looks like he was desperate to get a place in the test team. So of all the bowlers he was quite impressive.''
Gillespie might argue the point. He felt he had captured Bell's wicket late in the day and appealed confidently for a caught behind. He stood hands on hip and glared at the batsman from a metre away when the decision went in favour of the Englishman.
Bell said he would have reviewed it straight away had it been given out and if the technology was in use in the game. It is not.
While Wagner toiled hard for his two for 65 from 20 overs, Neesham had more success in the wickets column.
He took three wickets in the morning session, including the prized scalps of Kevin Pietersen and Jonathan Trott.
''It was very memorable. It was moving around a little bit with the new ball and that was definitely the time to be bowling,'' Neesham said.
''We did well to get a few wickets early. But I think they took the honours. If we had kept them to 30 or 40 less it probably would have been even.''