2:00 PM PT -- WWE has announced that Rusev will be replaced by Chris Jericho in the Casket Match vs. The Undertaker ... after Lana voiced a complaint.

"I’ve already spoke with WWE officials to change that match because I REFUSE to let my husband compete in a Casket Match," Lana wrote on social media.

Rusev added -- "Life is life ... it will be Rusev Day somewhere."

Unclear if this is a work or if an actual issue prompted Rusev's removal from the event. 

Stay tuned ... 

The Undertaker just smashed John Cena at WrestleMania, but his next opponent -- and his smokin' hot wife -- say he's gonna make the Deadman REST ... IN ... PEACE. 

We got superstars Rusev and Lana just hours after WWE announced Undertaker vs. Rusev at their Greatest Royal Rumble event in Saudi Arabia ... and the power couple told us Taker's about to take his last ride in the ring.

"Undertaker is a little bit in the past," Rusev told TMZ Sports at The Henry in WeHo. "I'll beat him so bad it may be his last fight."

Lana chimed in -- "You're gonna obviously crush him. He's stronger and faster and better." 

Rusev admits Undertaker's one of the GOATs, and has home-field advantage for their CASKET MATCH ... but says he ain't sweatin' it since "Rusev Day" is equally legendary.

We dunno, bro ... looks pretty intense.