Clowntime is over. Whatever the result on Saturday, Warren Gatland will finish the series against New Zealand with his coaching reputation encased in cement a month after an aside he made at the end of a media conference at which his methods had been questioned, which cursed the need for him to keep defending himself, was picked up on tape recorders and printed.

Some in the New Zealand media were quick to write off Gatland as a failure, despite his success with Wasps, Waikato and Wales, after the British & Irish Lions made a juddering start to the tour. That was a surprise, given the side virtually walked off the plane to the first match and were still acclimatising when they faced the Blues, never mind still gelling as a squad and a coaching team. It shows how in a time of instant judgment it sometimes pays to sit back and reflect.

Considering the lack of preparation time afforded the Lions by the four home unions, who further caved into clubs by agreeing that tours in future will be cut from 10 matches to eight, to take a series against the leading team in the world to the final weekend not only defies predictions but is an achievement it is difficult to overstate.

Yes, New Zealand played the final 55 minutes of the second Test with 14 players after Sonny Bill Williams was sent off but last season contained numerous examples of teams conceding a numerical advantage in the first half – Munster against Glasgow, England against Argentina and the Scarlets at Leinster in the Pro12 play-off semi-final – and winning.

And the Lions won by scoring tries. Before the start of the tour the former Lions and Ireland wing Shane Horgan, who questioned whether Gatland was the Lions’ weakest link, feared that Warrenball would be a case of hoping Owen Farrell landed his kicks while Beauden Barrett missed his – but it was the All Blacks who were reliant on penalties in Wellington.

“I am not sure Gatland has the playbook and the flexibility for this challenge,” wrote Horgan, who won his first cap under the New Zealander in 2000. And yet when Gatland named Johnny Sexton and Farrell in the side for the second Test, headlines accused him of being a desperate gambler, never mind that it was an option the Lions had considered from the moment the squad were named or that selection has been a strongpoint of his.

What was apparent from conversations at the squad announcement was that while Sexton and Farrell were unlikely to start together before the first Test, to give Robbie Henshaw and Ben Te’o opportunities to canvass their credentials, it was a partnership that could be activated from the bench and would definitely be tried in training.

Gatland showed in the selection for the second Test he was flexible and willing to change his mind. The tour until Wellington had largely been one of missed opportunities: the lack of finishing power hurt the Lions but in the soggy Cake Tin they fashioned the first try through long, precise passes that evoked England’s winning score in Cardiff in the Six Nations. Defenders were taken out to give the player out wide the space to finish.

The success Gatland has achieved as a coach is notable because he has been in charge of teams who are not frontline or fashionable: Connacht, Ireland, Wasps, Waikato and Wales, clubs and countries that lacked the resources of their rivals. He has always made the most of what he has had and it is easy to forget now just how mired in mediocrity Wales had become before he took over following an early exit in the 2007 World Cup.

One grand slam out of nowhere in 2005, which was immediately followed by a familiar implosion, was all they had to show from the new century. Graham Henry had returned to New Zealand before the end of his contract after the early promise of his reign faded into ignominious defeats and Steve Hansen, who changed attitudes by making players aware that professionalism meant a lot more than getting paid, was one defeat away from the sack before the 2003 World Cup.

Henry said this week he saw no reason why Gatland would not be a contender to coach the All Blacks in the future, although it would mean returning to New Zealand. He has two years left on his contract with Wales but he has become exasperated at some local media coverage of the national side, unable to figure out why headlines after a squad or a team announcement tend to focus on who has been left out rather than included.

He has drawn into himself in Wales after being free with his time in his first years there, largely because he wants to minimise his exposure to something he cannot control. Having said he will not be seeking a new contract after the 2019 World Cup, that is not going to change, sadly, because he had been willing to offer an insight into his thinking and methods and was always worth talking with.

He has been his old self on this tour, using the media to set his agenda and Hansen, unusually for him, made some acerbic remarks about the Lions unprovoked, aware that the All Blacks were facing their most demanding assignment since the World Cup.

When the Lions were last in New Zealand, they left with some questioning whether they would ever return given the one-sided series. Gatland has been part of the three tours since then and has helped salvage the reputation of the tourists: he has been involved in eight Tests, winning four and losing four; as coach, his record is 3-2.

Not bad for someone who is perceived to be tied to smash and drab. The scorn and mockery that greeted him on his arrival in his homeland has been replaced with apprehension as the Lions, having largely stopped New Zealand from playing without inhibition, stand on the threshold of only their second series victory in the country.

The third Test may prove to be a step too far, although Gatland’s teams have always had an adhesive quality, but whatever the outcome he should not feel the need to defend himself. Those who derided him as a mediocre coach should now appreciate the saying “notice what you see”. The former Waikato hooker is nuanced and layered, befitting someone who started coaching when he was playing. He knows there is more than one route to the top but having got there so often why is he so underestimated?

• This is an extract taken from the Breakdown, the Guardian’s weekly rugby union email. To subscribe, just visit this page and follow the instructions.