Undrafted rookie S Michael Thomas is a smart guy.

They don't just hand out degrees in sociology at Stanford University -- even to football players. 

So when Thomas looks at the 49ers' roster and then at himself in the mirror, he knows he's not looking at the team's newest starting safety.

But he does see a player capable of making the team's 53-man roster.

"I got to make plays on special teams and make sure the coaches understand that I know my assignments and that I can perform them on the field," Thomas said. 

Realistically, Thomas is a longshot. If he remains with the team, it'll likely be as part of the practice squad, a la three of his former Stanford teammates (C Chase Beeler, TE Konrad Reuland and OL Derek Hall) who all followed their former college coach, Jim Harbaugh, a few miles down Highway 101 last year.

A prep quarterback, Thomas arrived at Stanford without a true position, and it wasn't until current 49ers DC Vic Fangio arrived that Thomas settled in at safety. 

Thomas' familiarity with Fangio won't necessarily translate as far as the playbook is concerned.

"There are some calls that he would recognize and have a feel for, but not as much as you would think," Fangio said. "It’s a different game.”

Thomas said he hasn't yet resigned himself to the fact that the practice squad is a more likely option than the 53-man roster. Instead, he's opted to "shoot for the stars and maybe hit the moon."

He received some words of encouragement from someone who doesn't have to worry about making his team's roster on Monday -- No. 1 overall pick Andrew Luck, who served as a co-captain with Thomas at Stanford last season. Luck texted Thomas and said, "Go get that spot baby, put those pads on and make some noise."

Thomas and the other rookies suited up in pads for the first time as professionals Tuesday. Quarterbacks and other select veterans also took part in practice as they prepare for the veterans to arrive Thursday. 

The team's first official practice is Friday and its first full practice in pads is Sunday. 

Follow 49ers reporter Kyle Bonagura on Twitter: @KyleBonagura and @CBSportsNFLSF.