Shelton is insurance at center. My feeling that they would allow Allen one more year to prove he can play injury free was right. That said it was prudent to re-sign Shelton as insurance in case he doesn't this year. But in the long run, the Rams have extended Shelton twice now. He wants to be a starting center and he deserves to be if not here then elsewhere. That's why regardless of Allen, I see Shelton as the center going forward in 2024. Allen then becomes trade bait. Good centers don't come available often. Allen will be 29 next year.
Shelton will be a RFA next year. That means they have to extend him, tender him or allow him to walk. Shelton is 2 years younger than Allen and has proved he is a starting quality center. Believe me, there will be a market for Allen next year, he will be 29 and a proven starting center. A mid-round pick for a 29 yo starting center? If Allen is injured again this year, then Shelton takes over permanently which accounts for the language of his reworked contract. Next year he's a bargain as a starting center at about $4M on a second round tender. But they would be wise to simply sign him long term starting at $4M next year, which is half of what they would be paying Allen.
What makes Shelton a good center? He has good field vision and field awareness, i.e. he's cognizant of what is happening around him. There was a play where he was at RG where he came off a double team block with Havenstein, and picked up a delayed blitzing LB. It was a very good move by a veteran player. It also showed his ability to move and execute a block on the move. He still has an occasional tendency to lunge or can be inconsistent with his footwork. Those are things Wendell can correct since he was also a center in the NFL.