Cardiff head coach Matt Sherratt has been clear he sees Thomas as an inside centre.
But despite the competition, Thomas welcomes the return of Cardiff-born Sheedy from 10 years at Bristol.
The pair know each other well having attended the same high school, Corpus Christi, and played for the same youth team, St Peter’s, in the city.
Sheedy was also in the starting Wales team when Thomas made his debut against Canada in 2021.
“It’s nice to have Sheeds back. He hasn’t changed at all, he still just as loud as when we were in school,” said Thomas.
“He’s very good for us. He’s wise beyond his years, talks well and understands the game well. That’s just the sort of addition we needed.
“We played an exciting brand of rugby last season but you need to win. So we need to work on the basics to give that solid platform and control the game.”