CHICAGO -- White Sox manager Tony La Russa is out indefinitely as he undergoes medical tests in Arizona, according to the team on Wednesday.

La Russa, 77, missed Tuesday night's game against the Kansas City Royals after participating in regular pregame activities. Within an hour of first pitch, doctors advised him not to manage.

"We were trying to figure out what was going on," outfielder Andrew Vaughn said. "They mentioned a few things, maybe his heart, or something like that."

Bench coach Miguel Cairo will continue to manage until La Russa returns. He was at the helm for Tuesday's 9-7 loss to the Royals, Chicago's fifth consecutive defeat.

Cairo indicated that there was no incident after pregame which prevented La Russa from managing. Instead, it was La Russa's doctors who reached out and told him to stand down.

"He was fine yesterday," Cairo said before Wednesday's game against the Royals. "He was feeling fine. I talked to him today. He was fine."

The White Sox have had an underachieving season to this point, sliding in the AL Central. They were swept by the Arizona Diamondbacks over the weekend and have already lost the season series to the Royals.

La Russa has taken the brunt of the criticism for the team's failures.

"We have to do it for him," Cairo said. "He cares about this team. He really loves the Chicago White Sox. We have to do it for him."

Cairo indicated that he'll still be communicating with La Russa on a daily basis, if possible. There is no timetable for his return.

"He works really hard," reliever Kendall Graveman said. "That meant a lot to me as a player. He would show up every day and put in his best effort and really got after it every day."