Step one in crafting a mock draft is easy: Pass rusher Myles Garrett from Texas A&M widely is considered the most gifted player available, and the Browns, picking first overall, need an edge rusher.
It's at pick No. 2 and the 49ers where things get tricky.
The second-best player may be Alabama's Jonathan Allen. The problem is that he's an interior defensive lineman, the same position the 49ers have drafted in the first round the last two years. Few think they could take a defensive lineman three years straight.
Other connections between San Francisco's needs and draft talent are just as difficult to make.
The 49ers, for example, must restock their inside linebacking corps. The best player at that spot, Alabama's Reuben Foster, showed up at the scouting combine smaller than expected at 6-feet, 229 pounds, arrived with a shoulder injury, then was sent home early after a heated exchange with a hospital worker while he was waiting for an exam.
Malik Hooker didn't disappoint as far as size. The Ohio State safety, who had seven interceptions last year, measured 6-1, 206 pounds. But the 49ers seemed to indicate that Jimmie Ward would play the same free-safety spot that would be Hooker's natural position in San Francisco's defense.
LSU running back Leonard Fournette is intriguing. He would be more so if the 49ers didn't already have a similarly-sized running back on the roster in Carlos Hyde.
"Carlos is a guy who I was a fan of coming out of college," coach Kyle Shanahan said Wednesday. "He had a good career there. I looked at him hard when I was in Cleveland and I had a good feeling he was going to be a great back then. I don’t think he’s the finished product. There’s a lot more to his game. I look forward to us helping him bring that out.”
Finally, there's a huge need at quarterback. Shanahan said he's looking for a passer who processes information quickly and who doesn't flinch in the face of a pass rush.