Chicago, IL (SportsNetwork.com) - The first trade of the 2015 NFL Draft wasn't the one many were expecting.

The San Diego Chargers traded their fourth-round pick and 2016 fifth-rounder to move up two spots from the 17th selection to No. 15.

San Diego used that pick to select running back Melvin Gordon of Wisconsin. Gordon was the second running back selected in the first round, taken five spots after Todd Gurley of Georgia was picked by the St. Louis Rams at No. 10.

No running back had been taken in the opening round the last two years, the first time in NFL history that's happened.

The storyline coming into the draft was which team was going to trade up to No. 2 in the Tennessee Titans' spot and take Oregon quarterback Marcus Mariota. The Titans stayed put, however, and selected the Heisman Trophy winner with their original pick.

The 49ers, meanwhile, took defensive end Arik Armstead of Oregon.