But there are also differences between the two players. Unga saw a little action as a freshman in 2006 before getting injured early in the season and redshirting. He came back in 2007 and was the undisputed go-to running back for the Cougars from the very first game of the season.
Alisa, meanwhile, played linebacker as a true freshman in 2008 before serving a mission. His heart, however, was with a different position.
"I played tailback in high school, and it's always been my favorite spot," said Alisa. "When I got back [from my mission] I asked to move to running back, and they moved me to fullback, and after spring ball I asked them if I could move to tailback."
Still, playing behind established backs in seniors J.J. Di Luigi and Bryan Kariya, as well as sophomore Joshua Quezada, Alisa wasn't expected to be a big part of the offense. Just as Unga, prior to his injury in 2006, had to play behind Curtis Brown, Fui Vakapuna and Manase Tonga, Alisa would seemingly have to bide his time.
And with just three carries and four receptions through the first five games, that seemed to be the case. But then came last Saturday's game against San Jose State, when Alisa had 16 carries for 91 yards. As a comparison, Quezada had nine carries, Di Luigi had five and Kariya had three.
"I wasn't expecting that many carries," said Alisa. "They told me they were gonna give me some opportunities early on in the game, and they felt like I deserved just to have a shot. They said if I did well, they would give me a few more."
And do well he did, averaging 5.7 yards per carry. San Jose State, currently 94th among 120 FBS teams in rushing defense with 192.33 rushing yards given up per game, may not be the greatest barometer, but Alisa nevertheless clearly provided a much-needed physical presence.
"We've been looking for a back to run between the tackles, a physical presence from the beginning of the season to now," said Coach Mendenhall, "and Mike has been so impressive on special teams and so impressive in practice that it appeared over time that he deserved an opportunity."
Alisa hasn't had to carry the load in quite a while. His arms appear to be scratched up this week, likely part of the reward of getting so many carries last Saturday.
"I've been taking it a little slow, just trying to recover from a few bumps and bruises from the game," said Alisa. "But other than that, I've been working hard and just trying to keep my legs good."
The Cougar running game had been so meager in the first several games this year, and for numerous reasons. Lackluster run-blocking and a passing game that posed little threat certainly didn't help matters. Neither did an ankle injury that Quezada sustained prior to the season.
Still, the ground game had been making some progress over the past couple of games. But with the emergence of Alisa, the Cougars may have the featured running back they really need, a player that can provide a dynamic presence with a combination of speed and power.
"I would hope to see him in a continued role," said Mendenhall, who indicated that Alisa will have a similar workload against Oregon State this Saturday. "What he had, averaging over five yards a carry, is exceptional."
The Cougars, with only 116 rushing yards per game, are currently ranked 98th in rushing offense. But, there is some optimism that their recent success on the ground is a sign of things to come.
"I feel like the o-line is doing a great job and the running backs are responding as a whole, and it's fun to see when you see the team start clicking together like that," said Alisa.
Coach Mendenhall certainly saw things clicking together when Alisa provided a spark against SJSU.
"It was really fun being on the sideline and having the players, once they saw how hard he was running, that generated a lot of excitement and enthusiasm not only for him but for the team, and I think it affected the offensive line as well. I think they became more excited and [were] really enjoying the game more and finishing blocks because of how he was running the football and the physical presence that he was showing."