Along with Jonjo Shelvey, who is expected to spend the next 12 weeks on the sidelines, Emil Krafth Jamal Lewis and Federico Fernandez are also unavailable.
Krafth is a fresh injury for the Magpies after missing the opening day Premier League win over Nottingham Forest at St James’ Park.
Emil Krafth latest
“It was a strange one with Emil because there wasn’t really an injury,” Howe explained. “It was more just tightness.
“He felt he couldn’t open up. He’s had two scans and they’ve come back clear.
“I don’t necessarily think there’s an injury but maybe a problem with his back and stopping him opening up to full speed.
“Hopefully, that’ll be very short-term.”
Better news on Jamal Lewis and Federico Fernandez
Meanwhile, Lewis and Fernandez are back training with Howe’s squad having not played any part during pre-season.
However, it’d be a major surprise if either player was involved at the Amex Stadium.
“We’ve seen them training,” Howe said when asked about the pair.
“Jamal has done a couple of days - it’s great to see him back. He’s looked good.
“Fede, again, has done a couple of days this week. We gently re-introduced him because he’s broken down a couple of times, so we’re very keen to see him consistently train with us.
“Fingers crossed with Fede that he can do that and again, he’s looked very, very good. He is a top player.”
Jamaal Lascelles set to be available
Elsewhere, captain Jamaal Lascelles is on course for a place on the bench against Brighton.
The defender was a late withdrawal from the matchday squad versus Forest with a thigh issue.
Howe revealed: “He’s OK. (He) missed the early part of training and came back towards the end, so we anticipate he’ll be fit.”
Fabian Schar and Dan Burn, against his former club, are expected to retain their places at the heart of the defence.