"While he has been managing his symptoms, he hasn't done much conditioning. Once he gets a full week of conditioning in, we'll consider him for selection."
That means that all going well, Read could be available for the Crusaders against the Highlanders in Dunedin next weekend.
Read's concussion forced him out of the Crusaders victories over the Brumbies and Reds and tomorrow's match against the Sharks in Christchurch.
An earlier head injury suffered against the Hurricanes ruled him out of the win over the Lions in Johannesburg.
The lingering effects of the latest injury would have caused concern for Blackadder and All Blacks coach Steve Hansen with the first test against England on June 7 rapidly approaching.
But Wednesday's news will have come as a relief to both.
In the meantime, Luke Whitelock is providing very good cover for Read at the Crusaders, and Blackadder says the 23-year-old's potential is coming to fruition.
"He's become more dynamic on defence and is having a big influence in matches."
With giant wing Nemani Nadolo providing a threat the Crusaders haven't had in the backline for years, Blackadder's team is looking much more balanced.
But although the Crusaders have won their past five matches to rocket into a play-off position, Blackadder is aware of the need to keep the foot on the accelerator.
"It's a week by week thing because if we don't front against the Sharks we're back almost to square one," he said.
"We know what we'll get from the Sharks - a fair bit of kicking and a team which will be determined to take us on up front so we have to meet fire with fire."
Tom Taylor, also a recent concussion victim, replaces All Black Israel Dagg at fullback, and Willi Heinz will start at halfback in his 50th match for the Crusaders.
Dagg has been managing a knee problem.
Said Blackadder: "We've been really happy with the way he's been playing, but there are some early signs of wear and tear and we just want to make sure that we manage that so that he can continue to play at his best."
