Johnson (17-5) enters the bout off an impressive first-round knockout of Pat Barry on May 5 in East Rutherford, N.J. It was the second straight win for Johnson in UFC competition.
He came into UFC on a two-fight losing skid with Strikeforce. Despite his Octagon success, Johnson pondered the offer from UFC officials to face Struve on short notice.
"There was a little bit of hesitation," the 6-foot-4 Johnson told ESPN.com. "This is a big opportunity but if you don't gamble, you can't win.
"After my last fight, I took a week off, but I didn't barbecue and drink beer like I usually do. After a week off I was back at it.
"I'm at the UFC level now. I wanted to stay sharp. I knew something would come up quick. I didn't know this quick."
Johnson had a height and reach advantage against the 5-foot-11 Barry. But he will be on the short end of both those categories against Struve.
At 6-foot-11, Struve is UFC's tallest competitor. He has a reach of 84 inches to Johnson's 81.
"He's tough. He's good on the ground. He's durable," Johnson said of Struve. "I've watched a lot of his fights. He takes a beating and he comes back to win.
"But I'm going to push the pace. He leaves himself open a lot, and I only need a few punches to land."
In his most recent bout on Feb. 15, Struve knocked out Dave Herman in the second round. He has a pro mark of 23-5 and has won two straight.
A knee injury suffered during training camp forced Hunt out of the fight.
Information from ESPN.com's Brett Okamoto contributed to this report.