I came across the below sentence from my English textbook:
He's only young, but he's learning fast
The structure 'only...but' is quite strange to me. I also found another example on Givemesport.com website
In charge of Manchester United, Ferguson was keen to bring Oxlade-Chamberlain to the club - and even sung his praises when asked about the possibility of signing him.
"Alex Chamberlain is only young but he has potential," said Ferguson.
I guess that the meaning of the structure 'only...but' is similar to 'not only...but also', like:
If this project fails it will affect not only our department, but also the whole organization.
Is my guess correct?