“He missed last year [while on contract in Japan] and he was really excited about being in a Blues jersey this year.
“I thought he was really starting to hit his straps, with his form and his leadership, and he is a key player in our team. He’s a huge loss to us.”
Tuipulotu played the full 80 minutes against the Highlanders, scoring the only try of the game.
MacDonald wasn’t aware his powerhouse forward was injured until well after fulltime.
“I was speaking to him after the game for 10 minutes, and he didn’t say a thing, then 20 minutes later in the sheds, he’s walking around with a cast,” the coach said.
“He’s not a man of a lot of words and didn’t even say he had a sore arm but he obviously finished the game with it broken and didn’t speak of it afterwards.
“He’s a tough, old rooster, but the boys are definitely disappointed for him.”
The injury comes three weeks after fellow-Blues lock Sam Darry suffered a broken forearm, also ruling him out of the rest of the championship.
MacDonald is likely to call on the versatile Tom Robinson and Cameron Suafoa to the lock for the remainder of the campaign.
Meanwhile, first five-eighth Beauden Barrett is poised to return to action after recovering from a cut to his foot that sidelined him for two weeks.
MacDonald said the All Blacks playmaker looked “sharp” at training on Monday.
“If we really wanted to push him to the limit, we could have put him out last weekend. Just the extra few days will make sure the wound has healed properly and didn’t open up.”
