The Nationals viewed DeJesus as an upgrade over Bernadina, who hit .178 with a .247 on-base percentage and a paltry .517 OPS in 152 at-bats this season.
In 284 at-bats with Chicago this season, DeJesus hit .250 with a .330 on-base percentage, playing primarily center and left field.
How and when DeJesus would be used, however, remained unclear.
Johnson said he was surprised by the timing of the move, noting multiple times during his news conference that the Nationals were in a less-than-desirable place in the playoff picture, 9 1/2 games back in the wild card and 15 1/2 back in the National League East.
“He’s a quality player,” Johnson said of DeJesus. “If anybody gets hurt, he can step right in and play at a high level. You can never get enough quality players. Rizzo has done a great job of picking up quality players.
“He doesn’t have anything he needs to prove to me. I’m sure that he wants to play. But [Bryce Harper] needs to play, most definitely. [Jayson Werth] is having an outstanding season. [Denard Span] is doing a great job defensively, his bat is picking up. I’m more concerned, with where we’re at in the standings, getting the young guys more at-bats than some of the veteran-type players.”