Borthwick has no qualms over starting undercooked Slade against All Blacks
Slade will face the All Blacks after just 55 minutes on the field for Exeter following shoulder surgery, with the 31-year-old only making his comeback against Harlequins on Sunday.
Slade, however, is a key figure in England's 'blitz' defence and Borthwick believes the 65-times capped midfielder is ready for the challenge of facing the All Blacks again after his side were twice narrowly beaten during a two-Test series in New Zealand in July.
"Sladey is a really important player for us," said Borthwick after announcing his team on Tuesday. "He's an experienced Test match player and he's in fantastic condition.
"With the shoulder surgery he's had, he's been able to be run. He's as fit as I've ever seen him.
"He feels in great shape. He's a player who is energised and he'll go really well on Saturday."
Spencer starts
Meanwhile the absence of the injured Alex Mitchell has paved the way for scrum-half Ben Spencer to make his first Test start.
All of six previous caps, including a brief appearance in the 2019 World Cup final, have come off the bench but Spencer's form with Bath this season means he will at last be involved from the kick-off.
"He's such an experienced player," said former England captain Borthwick of Spencer. "He knows how to deliver on the biggest of stages and that's important. He's a calm guy and a leader with his club."
Borthwick added flanker Ollie Chessum will miss the whole of a November programme that also includes fixtures against Australia, South Africa and Japan after the Leicester forward, set to feature at blindside flanker, underwent knee surgery on Monday.
Chandler Cunningham-South fills the vacancy, with Sam Underhill not even among the replacements after featuring in the back row in all of England's previous eight Tests.
Borthwick said Underhill's absence was down to an early season ankle operation, which the England coach said had limited his effectiveness for Bath.
"When you have an ankle surgery you can't be on your feet and so much of Sam's game is that constant work rate, particularly in defence," said Borthwick.
Veteran playmaker George Ford provides fly-half cover after Marcus Smith was given the No 10 shirt.
England are seeking a first Twickenham win over New Zealand since 2012.
"We're excited for the challenge of playing against one of the best teams in world rugby," said Borthwick.
"We'll need to be accurate, keep our discipline and maintain a level of intensity throughout the match, from the first whistle to the final moment."
New Zealand, who thrashed Japan 64-19 in Yokohama last weekend, are due to name their side on Thursday.
