"The schools that have offered me all want me to play tackle, but a lot of the bigger-level schools I've been talking to see me as a guard or maybe even center," he said.
This versatility has helped Callen's recruitment this summer.
"So far I'd say my recruitment is going really well," he said.
"My spring and early summer went really well I think. Coming out of last season I was kind of an unknown prospect and a lot of coaches told me that in order to get their attention I'd have to show them senior tape, but slowly my name got out after I did a few combines and workouts and my recruiting just really picked up."
Callen has seen a number of scholarship offers come his way this offseason.
"Right now I have offers from Toledo, Ball State, Bowling Green, Central Michigan, Western Michigan, Eastern Michigan, Ohio, Wyoming, NIU, and North Dakota State."
Along with his offers, Callen has been hearing from a couple of BCS teams.
"I've also been hearing from Big Ten schools like Illinois and Minnesota," said Callen.
With so many offers, Callen has plenty of research to do before making a decision.
"I really look for a school that has a nice atmosphere," he said.
"I try to take in the feeling of both the campus and the town that the campus is in. I also like schools that take pride in their facilities. Schools with the best athletic facilities tend to be ones that take a lot of pride in their athletics and that's something I really like," he added.
Without visiting many of the schools on his offer list, Callen does not have a clear list of favorites.
"Right now it's hard to say, I really want a chance to see all the campuses before I can really choose a favorite," he said.
"However, my uncle played at NIU and so did his brother. My mom and aunt also went there. I wouldn't say it's a favorite, but it's definitely the school I know the most about."
Another school that Callen is interested in is Minnesota, a school he camped at this summer.
"I am extremely interested in Minnesota," he said.
"When I went to the camp I connected really well with the coaching staff. Coach Limegrover, the offensive line coach, had a great coaching style and I really felt that I learned well from his style. Coach Zebrowski is also a really down to earth coach. I also had a chance to talk to Coach Kill for a little too, he is just a great guy. The overall feeling I got from the campus, the staff, and the city was just great."
Although he does not yet have an offer from Minnesota, Callen feels that one could be coming his way.
"From the feedback I have been getting from the staff lately, I think that could definitely be a possibility," he said. "It all just depends on what happens with other prospects. I understand that instate kids should be a main priority but at the same time I know that I value the school and program just as much as any prospect."
Even though Callen is still waiting on more offers, he plans on making a decision soon.
"I'm really shooting to commit before the first game," he said. "There's a chance I may extend that so I can show a few schools senior tape, but right now that's what I'm shooting for."