When UFC officials needed a last-minute substitute to fight a Russian on a winning streak, they called a former Army sniper.

But before unbeaten Andrew Todhunter can square off with Albert Tumenov in Mexico City on Saturday as part of one of the biggest UFC cards of the year, he's got one other enemy to deal with: The scale.

"I have to lose 41 pounds in eight days," Todhunter (7-0) said Wednesday, two days before the weigh-in for UFC 188, where he'll make his debut for the promotion. "I don't care who you are or what you do, but to even get half of that off of a normal person, or an athlete, will break them."

Todhunter said that a little more than a week ago, when he received word that Hector Urbina's injury would open a spot on the card to fight Tumenov, he tipped the scales at 211 pounds. In the middle of last month, he won a boxing match at the 197-pound limit. He usually cuts down to 185 for MMA, but will fight at 170 come Saturday.

"I'm down in the 180s right now," Todhunter said Wednesday. "I can feel myself getting dry, but I'm going to keep pushing."

U.S. service members pose for a picture with their musical instruments, during the RC-East end of mission ceremony at Bagram Airfield, Afghanistan, Tuesday, Nov. 4 2014. RC-East is the last Regional Command to transition to a Train Advise and Assist Command and this will be one of the last transitions as all of the ISAF units transition to the Resolute Support Mission. (AP Photo/Massoud Hossaini)
U.S. service members pose for a picture with their musical instruments, during the RC-East end of mission ceremony at Bagram Airfield, Afghanistan, Tuesday, Nov. 4 2014. RC-East is the last Regional Command to transition to a Train Advise and Assist Command and this will be one of the last transitions as all of the ISAF units transition to the Resolute Support Mission. (AP Photo/Massoud Hossaini)

He said he's relying on his Army training for this punishing task — but not the physical part.

"I feel like it's a mental battle, more than anything," Todhunter, 27, said. "And I feel like a lot of the courses in the Army make you mentally tough. I'm glad I did those things in my life, because they definitely help me now."

Todhunter left active duty in 2009 as a corporal, having deployed once to Iraq in 2007 with 2nd Battalion, 16th Infantry Regiment, 4th Brigade Combat Team, 1st Infantry Division out of Fort Riley, Kansas. His time on active duty ended after a long stay in a warrior transition battalion following a serious hand injury in Iraq, one that would require multiple surgeries and piles of paperwork.

"It took a year and a half to do [the surgeries]," Todhunter said. "After all that, my [expiration term-of-service] date comes. I just said, 'I'm going into the reserves.' "

Before he left, "The Sniper" became a poster boy of sorts for snipers when it came to Army recruiting. His image still pops up at recruiting stations, and he was featured in a short video — although he spends much of it hidden away.

The Air Assault School graduate participated in combatives throughout his Army career and began fighting as an amateur in 2009. He turned pro in 2011 and hasn't gone the distance since, winning all his fights by submission. His last bout, an all-military clash with Levi "The Marine" Avera under the Legacy Fighting Championship banner, took a little more than three minutes.

Tumenov (15-2) represents a drop in weight class but a rise in competition level. The Russian, nicknamed "Einstein," is 3-1 in the UFC and hasn't lost since his February 2014 debut. While Todhunter lives by the submission, 10 of Tumenov's 15 wins have come by knockout.

"I'm an explosive grappler, I'm an explosive wrestler, and I hit really hard," said Todhunter, who enters the fight as a heavy underdog — about 4-to-1 on some gambling websites. "I'm mentally tough, and I think I'll always have opportunities. … There's always opportunities to win this fight."

Andrew "The Sniper" Todhunter

Photo Credit: Courtesy of Guardian Sports Group

Saturday's bout is the first on a four-fight deal, but the Oklahoma native was already making future career plans: Now a college graduate, Todhunter said he began the required paperwork to return to service as an officer just days before taking the UFC contract. One of his two degrees is in organizational leadership, he said, and he feels he's got more to give in uniform, albeit in a new role.

"I feel like I've put myself in the right place to go back and finish my career," he said.

Todhunter's fight will be on the preliminary card for the pay-per-view event and will be available via the UFC Fight Pass streaming service beginning at 6:30 p.m. EST. UFC heavyweight champion Cain Velasquez will return from injury to fight interim champ Fabricio Werdum in the night's main event.