Sam Mellinger details the adjustments Mark Teahen made to his swing in his stint at AAA:

Teahen’s strength had always been on the outer half of the plate. Big-league pitchers knew this, so they stayed inside. Teahen now admits this got in his head. He thought too much about the inside pitch, stopped laying off it, and then started missing the outside pitch, too.
Omaha hitting instructor Terry Bradshaw made a video of Teahen’s good at-bats from last year. What better way to teach a stubborn student than to let him learn from himself? The mechanical changes were subtle. They shortened Teahen’s swing, kept his hands back, and made a minor adjustment with his hips that allowed him to hit inside pitches better.
Once he did that, the Royals had no choice but to call him back up. He was 28 for 56 with a 1.107 slugging percentage and .606 on-base percentage in his last 17 games in Omaha.
“I want you to know it’s nothing that I really did, it’s what Mark did,” Bradshaw says.

Teahen’s adjustment now gives the Royals depth at third base, something they should be able to exploit to their advantage.