White will return from ODI duties to lead the Renegades in Friday night's semi-final against the Adelaide Strikers at Adelaide Oval.
The Renegades lost their only encounter with the Strikers this season, but Adelaide will lose star players Travis Head, Alex Carey and Billy Stanlake to international duties for Friday's clash.
"We've got momentum, we're playing some really good cricket and we welcome back Whitey, who has been outstanding," Cooper told reporters on Monday.
"To have someone like him come back into the team with the experience he brings for such a big game will be priceless.
"We had a few disappointing losses but to win the last two ... I reckon we've got some good momentum at the right time.
"It's going to be very disappointing if we don't (win the title)."
The Renegades will also lose a key player to the Australian Twenty20 squad in seamer Kane Richardson, while former Strikers skipper Brad Hodge is unlikely to play again this season after he was struck down by appendicitis.
Cooper and skipper Aaron Finch, also absent due to international commitments, are the only two current players to feature in the Renegades' only finals appearance in the BBL's second season.
The Brisbane Heat's Luke Pomersbach carted the Renegades' attack to all parts of Etihad Stadium in that semi-final in a match-winning 112 not out.
The Renegades have been perennial underachievers since, but Cooper, one of the club's longest-serving players with 45 games, believes the current line-up is the strongest he's been a part of.
"Our depth has been a bit of an issue once we've lost our Australian players in the past," he said.
"They've done a great job with this squad ... we've got guys who were sitting on the bench ready to go who have a fair bit of Big Bash experience.
"To have them come into the side and perform pretty much straight away has been good."