The Orioles designated Rivera for assignment Tuesday.

Rivera was already being used sparingly and his playing time was set to be cut even more with Jordan Westburg (hamstring) back in the fold. The 28-year-old has been outrighted previously, so he has the ability to elect free agency if he clears waivers again.

The Orioles activated Westburg from the 10-day injured list Tuesday.

Westburg is finally ready to rejoin the Orioles' lineup after being sidelined since late April with a left hamstring strain. He looked sharp in eight rehab games with Triple-A Norfolk, going 11-for-28 with a pair of home runs. Westburg will regain his status as the Orioles' everyday third baseman.

Urshela (hamstring) is expected to be sent out on a minor-league rehab assignment later in the week, Martin Gallegos of MLB.com reports.

Urshela, who was placed on the 10-day injured list May 23 due to a left hamstring strain, is set to begin a rehab stint with Triple-A Las Vegas. It's been just over two weeks since his last game action, so he should only need a handful of at-bats in the minors before the team feels comfortable activating him.

Rengifo is not in the lineup for Monday's game versus the Athletics.

Rengifo is stuck in a season-long slump and has been particularly brutal at the plate lately, going 3-for-30 over his last nine contests. Kevin Newman will hold down third base and bat ninth in Monday's series opener.

Triple-A St. Paul placed Fitzgerald on its 7-day injured list Sunday due to a right ankle sprain.

Fitzgerald was hitting just .159 with a .525 OPS in 12 games since he returned to Triple-A from his brief time in the majors. He's hitting .284/.378/.467 with five home runs overall in 47 games at Triple-A.

Harris (undisclosed) went 2-for-4 with a double and a run scored Saturday in his return to the Triple-A Las Vegas lineup after being activated from the 7-day injured list Friday.

Harris had been out of action at Las Vegas for nearly two months before making his return from the shelf. The 26-year-old third baseman is slashing .382/.462/.636 with three home runs and three stolen bases in 65 plate appearances at Las Vegas for the season and could merit consideration for a promotion to the Athletics if he can maintain a good run of health.

Vargas went 1-for-3 with a home run, a walk and three RBI in Sunday's 7-5 loss to the Royals.

Vargas gave the White Sox an early lead with a two-run homer in the first inning and later added an RBI with a bases-loaded walk in the ninth. The long ball was his first in eight June games, during which he's gone just 5-for-24 at the plate. On the season, the 25-year-old is slashing .237/.319/.421 with nine home runs, 29 RBI, 30 runs scored and one stolen base across 257 plate appearances.

Lee went 2-for-3 with a walk and a solo home run in Sunday's 6-3 win over Toronto.

Lee tied things up at 3-3 in the fourth inning when he took Bowden Francis deep to right field for a solo home run. During his 10-game hit streak, Lee has slashed .317/.349/.415 with one steal and six RBI across 43 plate appearances. His strong play at the plate should keep Lee in the Twins' starting lineup even with multiple players returning from the injured list.

Mayer is out of the lineup for Sunday's game against the Yankees, Mac Cerullo of the Boston Herald reports.

With southpaw Carlos Rodon taking the hill for the Yankees, the left-handed-hitting Mayer will retreat to the bench after going 2-for-3 with a solo home run and an additional run in the first two contests of the series. Abraham Toro will replace Mayer at third base.

The Yankees claimed Alexander off waivers Sunday and optioned him to Triple-A Scranton/Wilkes-Barre.

Alexander had been with the Athletics' organization this season until he was DFA'd on Thursday. The 28-year-old went 3-for-17 over six games with the Athletics but posted an .866 OPS with 10 homers, 32 RBI and two stolen bases over 180 plate appearances with Triple-A Las Vegas.