"[Teams] want to be adding to their ballclub and still be in the pennant race in September," executive vice president of baseball operations Dan Duquette said. "We've been fortunate; we've had a number of guys have great years. We've got some excellent leadership from [manager] Buck [Showalter] and the coaches, and this is why we do this, right?"
De Aza is batting .243 with five home runs and 15 stolen bases for the White Sox this season. He is expected to report before Sunday's game.
"He's a multi-talented outfielder," Duquette said. "He's good in left, he can play center field, he had two very good years in '12 and '13, where he hit for power, and he gives us a veteran outfielder who we can use to supplement our team."
Johnson began the season with the Yankees and was traded to Boston at the Trade Deadline for Stephen Drew. He is batting .212 with six home runs this season. The infielder has played for every other team in the American League East.
Both Duquette and Showalter expect him to join the club on Monday when rosters can expand to 40 players.
"He's a veteran infielder, he can play a couple of different positions and we've been trying to balance out our lineup with the addition of some left-handed bats," Duquette said. "And we were able to acquire two veteran bats to help us."
In his career, the left-handed-hitting De Aza has hit 30 of his 35 home runs against right-handers. Johnson is batting .216 against righties this year compared to .194 against left-handed pitching.
De Aza, in particular, has proven himself a capable offensive player. In '12 and '13, De Aza totaled 26 home runs. All five of his homers this season have come against righties.
"He's very good against right-handed pitching. That's his strength," Duquette said. "He can play the outfield. He's a good defensive outfielder in left, and he can run and he can steal a base."
De Aza gives the Orioles a bit of extra outfield depth following a season-ending injury to Manny Machado that forced Steve Pearce to move from left field to first base full-time. Pearce also suffered an injury on Friday, but he's not expected to land on the disabled list.
De Aza would lead Baltimore in steals and provides the O's with another solid defensive player. At the very least, he can provide the Orioles with an upgrade over David Lough, who has served as a pinch-runner, defensive replacement in left field and backup center fielder to Adam Jones.
Johnson, on the other hand, provides versatility as his greatest asset. Since Machado landed on the DL, infield depth has been a clear weakness for Baltimore. In the short term, Pearce's injury exacerbates that concern. Johnson can play first, second, third and the outfield.
"Kelly's well-traveled and he can play a couple different positions," Duquette said. "He's got some power and he can get on base and he can hit right-handed pitching, and that gives us some more options to help our ballclub."
Almanzar, the other player the O's acquired in the Johnson deal, began his career with the Red Sox, but began the season with the Orioles after being selected in the Rule 5 Draft. He started the year on the DL and was returned to the Red Sox at the start of July when he finished a rehab stint. He had been playing with Double-A Portland.
As for the players Baltimore gave up, Chalas had been playing with Triple-A Norfolk, Blackmar has played the entire season with Class A Advanced Frederick, Weeks played three games with the O's and had been with Norfolk, and De Jesus Jr. also spent the entire year with Norfolk.