The Cubs will be without Clint Frazier for at least a week.

The outfielder has appendicitis and was placed on the 10-day injured list Friday afternoon (retroactive to April 20).

“Still running a lot of tests,” manager David Ross said Friday morning. “He hasn’t had surgery yet. We’re keeping him in our thoughts.”

Frazier has appeared in 10 of the Cubs’ first 13 games, making starts at DH and in left field. He is hitting .143 with 2 doubles and a pair of walks in 24 plate appearances.

The 27-year-old looked poised for a potential breakout season during Spring Training but the Cubs had a crowded outfield picture and now the injury throws a wrench in that for Frazier.

There is no timeline on when Frazier will return to the Cubs but will be out until at least early May.

Meanwhile, the Cubs have a new arrival in the clubhouse — beyond Sean Newcomb.

Alfonso Rivas was called up to Chicago to take Frazier’s spot on the roster.

Rivas, 25, broke camp with the team and went 2-for-4 in 2 games before being optioned to Triple-A last Saturday. He has been raking in 3 games since being sent down, hitting .539 with 2 doubles, a homer and 4 RBI in 14 plate appearances with Iowa.

[MORE: ‘It means everything’: Alfonso Rivas relishes first Opening Day with Cubs]

Rivas adds another left-handed bat into the equation and can play first base or corner outfield.

In other injury news, Alec Mills (back) is scheduled to throw a rehab outing with Triple-A Iowa Saturday. Wade Miley (elbow) threw another bullpen Friday and is building up to facing hitters in a live bullpen/simulated game (though no date has been set for that).

Both veterans would provide a boost to the Cubs pitching staff when they return to health.

Infielder Andrelton Simmons has been slowed by a shoulder injury since he signed with the team in mid-March. He continues to throw and hit at the Cubs’ complex in Arizona.

On the roster front, outfielder Greg Deichmann has cleared waivers and been outrighted to Triple-A Iowa. The Cubs designated him for assignment last week to clear room on the 40-man roster.