Leon MacDonald, who has been coaching Tasman for the last two seasons, said returning to Blenheim was the reason he wanted to cut his ties with the Crusaders.

Having sacrificed a prime job at the Crusaders for family reasons, Leon MacDonald has signed a fresh two-year deal with Tasman.

Rarely do coaches abandon a successful team, especially one that has just won a Super Rugby title, but after completing one season of his two-year deal as an assistant backs coach at the Christchurch-based club MacDonald has opted to return with his wife and four children to Blenheim.

The unexpected loss of MacDonald, who had the Crusaders' backline firing through the season, forces head coach Scott Robertson to search the market for a replacement.

KAI SCHWOERER/GETTY IMAGES Crusaders Head Coach Scott Robertson has a tough search ahead.

Assistant forwards coach Jason Ryan and another assistant backs coach, Brad Mooar, have confirmed they will stay.

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Given the Crusaders have a reputation for digging into their local stocks when signing coaches, the job of replacing MacDonald may have been simplified if Joe Maddock, currently the Canterbury assistant backs coach, had been asked to jump into a Super Rugby role.

SUPPLIED Tasman CEO Tony Lewis can't believe his luck over MacDonald's move.

But a recent flurry of activity in the market has complicated that scenario.

Earlier this week Maddock was appointed head coach of Canterbury for 2018, because his current boss, Glenn Delaney, announced he was joining the Highlanders as their defence coach for 2018-19.

The day after the Delaney deal was made public, Jon Preston, a former All Blacks and Canterbury halfback, announced his resignation as the Highlanders high performance and skills coach and could be a potential option to replace MacDonald.

Undoubtedly, the biggest winner in all of this has been Tasman.

It was expected MacDonald would focus solely on his Crusaders job when his Tasman contract expired at the end of the Mitre 10 Cup. Instead he has re-signed through to the end of 2019, and it is understood his assistant Andrew Goodman is being groomed as his replacement once that term expires.

"Stepping back from the Crusaders assistant backs coach's role was certainly not an easy decision to make," MacDonald stated. "However, the family's preference is to be living back home in Blenheim, so that is absolutely where I need to be."

Crusaders chief executive Hamish Riach said his organisation were still aiming to employ MacDonald in a resource coaching role that allows him to remain based in the upper South Island.

"We understand and respect his reasons for stepping aside to allow him to remain with the family in Blenheim, and we are just happy he is still keen to be involved," Riach said.

MacDonald's short tenure with the Crusaders resulted in them having the most potent attack in Super Rugby; they dropped just one competition game and beat the Lions in the final in Johannesburg.

Tasman CEO Tony Lewis couldn't believe his good fortune when MacDonald, who is in his second year of being head coach of the province and guided the team into the final last year, said he wanted to renew his contract for two more years.

"Leon wants to be a head coach and in my belief he is an exceptional one," Lewis said. "And the best way for him to be a head coach of Super Rugby is to be coaching Mitre 10 Cup."