I started paying attention to Coker when he was at FSU, after the rumors started of his transferring to Alabama. He clearly had potential, but he also has room for improvement. I thought he'd come in and take over the job, I felt that was the plan, but I also found myself defending Sims a lot vs. the people that were overplaying Coker's abilities. Yes, Sims had a couple shaky A-Days, but on the field his numbers were actually a bit better than Coker's. However! Now I'm on the other side, Coker showed development and improvement, if that was the case again then I think he'll be a good starter.
I think a lot of people forget Coker had a season ending injury in 2013 and this had to have hurt his development a bit. He had to kind of tie rehab to adjusting to a new school and coordinator, he just didn't make that leap as cleanly as I guess everyone might have liked. However, just compare these:
2014 Completion %: 64.4 Yards: 403 TDs:4 INT:0 SACKS:3
2013 Completion %: 50.0 Yards: 250 TDs:0 INT:1 SACKS:5
That's across the board improvement. I fail to see why people are worried about him. Also, if you want to see how solid those stats are, that's a better season leading up to starting than AJ, Blake or GMacc had. Only GMac had a better completion percentage, but he only attempted 11 passes (one of those an INT), Coker threw for more yards, more TDs, and had a good rating.