The display of power wasn't surprising to Nationals manager Matt Williams, who was part of the D-backs coaching staff when Upton played in Arizona.
"A dynamic player. Does a lot of things right," Williams said. "Stras missed with a fastball kinda up and in for the homer. Tanner did as well. You make a mistake to a guy with power like that, sometimes you can pay."
In 20 games and 72 at-bats at Petco Park this season, Upton is hitting .375/.425/.764 with eight home runs and 20 RBIs.
This is nothing new for Upton, who will be a free agent after the season. His career line in San Diego in 241 at-bats is .307/.369/.577 with 16 home runs and 37 RBIs.
"He's got real power, all-field power. He's a guy who hits homers. He gave us a little cushion with the first homer," said Padres manager Bud Black.