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.
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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.
The best fit when it comes to that criteria may be North Carolina's Mitch Trubisky. The issue: Trubisky only started one season for the Tar Heels.
"The more tape the better, the more confident you feel in it," Shanahan said of evaluating players. "A year’s tape is pretty good, you get to see a lot. But when people have done it over time, it makes it a lot easier to make some of the decisions we have to make. You only get so many draft picks."
Receivers wanted -- One area Shanahan and the 49ers are sure to upgrade: Wide receiver. The team's top two players from last season, Jeremy Kerley and Quinton Patton, are scheduled to be free agents on Thursday, and neither came close to 1,000 receiving yards last year.
Shanahan was lukewarm in his praise of the group.
“No one in particular,” he said when asked who stands out. “I feel we’ve got a bunch of good players we feel we can compete with, and we know we need to add some, too. We’re going to add as many as we can to help our roster."
That likely will start in free agency.
The 49ers have been linked to the Bears' Alshon Jeffery, while Cleveland's Terrelle Pryor or Washington's Pierre Garcon -- who has a background with Shanahan -- also make sense.
The two top receivers in the draft, Clemson's Mike Williams and Western Michigan's Corey Davis, did not run at the combine but said they will do so at their pro days.
Cal's Chad Hansen, who could be taken as high as the second round, ran his 40-yard dash at in unofficial times of 4.54 and 4.57 seconds. That's not bad for someone who measured 6-2, 202 pounds with 10 1/8-inch hands.