"Obviously, it's a bummer that he's not here, because it was such a fun duo to be able to work off one another and things like that, whether it be practice or games," Thielen said Thursday on KFAN, according to Chris Tomasson of the Pioneer Press.
"So, I'm definitely going to miss that, but it will be fun to see him have success somewhere else," he added.
Beginning in 2016, Thielen and Diggs established themselves as one of the NFL's most feared receiving pairs.
They each went over 1,000 yards and caught nine touchdowns in 2018 and they helped the Vikings reach the NFC title game in 2017.
Though Diggs is no longer his teammate, Thielen said the two won't lose touch.
"We've talked since he got traded," he said. "He is one of my good friends and will be for the rest of our lives."