He was great in Poco and even better in the Eagles.

...excellent, high clear choices. Randy Meisner had a wonderful voice too.
In fact, one of the things that caused the rift between him and Frey/Henley was his reluctance to sing lead live, especially "Take It To The Limit". They froze him out; he told them buh-bye.
Then, they got Schmidt who is the same guy that replaced him when he left Poco.
It was like Poco was a farm team for The Eagles.

I don't remember his name, just that I really liked him and the songs he wrote with Poco. He was a rhythm guitarist. Ug, I hate it when my old brain fails to come up with important names.

I can't even guess who it would be. A drummer maybe?

Ta da - Richie Furay - singer, songerwriter and guitarist was one of the original founding members of Poco but left in 2016.

I KNEW IT! Loved Furay in Poco and his too short stay as an Eagle.

...Furay ever played with them. By 2016, their musical style & him wouldn't seem to be a fit.
Richie isn't listed in the WIKI page on The Eagles.
His stay must have been very short.

At first it seemed like a good match, all great country rock, but that changed and Furay left. I was living in CA at the time, married to a musician, so followed the music scene there very closely, being involved in some of it. I also was a huge Richie Furay fan from him being in Poco - he wrote such beautiful songs.

Edit - fixed fat finger error

Thanks to OP for posting it!