After his successful 11-month fight against cancer, well-loved sideline reporter Craig Sager Sr. is battling leukemia again, his family revealed on Sunday.

On his Twitter page, Sager's son, Craig Jr., announced that his father is gearing up for another round of treatment. "[Sager] Sr. is battling his newest set of obstacles, but unlike the first time when everything was new, there is a blueprint in place and all focus is on one checkpoint at a time. Sr's leukemia returned last week and he is undergoing a treatment that will be much like this time last year when he got rounds of chemo and prepared his body for a bone marrow transplant," Craig Jr. said.

He added that his father has flu but his fever went down so he was able to go home a day prior to his return to the outpatient treatment.

"Beating the flu is a main priority right now. There are constant changes as we learned from the last 11 1/2 months but we will try to keep you as up to date as we can," he noted.

Due to his illness, Yahoo Sports said Sager had to cancel plans on some NCAA tournament games for TNT and TBS where he is currently working.

It can be remembered that Sager took a leave of absence from work after he was diagnosed with acute myeloid leukemia in April 2014. His doctors cleared him of cancer just recently, prompting him to return to work in early March, during the match between the Chicago Bulls and Oklahoma City Thunder, Bleacher Report noted.

He said, "I'm very grateful, very thankful, and I got up today and it was like the first day of school. You're a little nervous. I've done it before but everything's a little different. It's a long 11 months, believe me." 

Sager added that he kept a positive attitude, listened to his doctors and he tried not to "think about the negative things." He was looking forward to go back to work, in fact, he got a new set of wardrobe since he lost weight during his first cancer ordeal.

"I'm back. A little bit lighter, I don't know if you can see it on TV but I lost close to 50 pounds, got some of it back, but I had to get some new clothes because all those great things I had before don't fit anymore," he said, as quoted by ESPN  .

Sager also noted that he was in "total remission" as ESPN said that his son Craig Jr. donated some of his bone marrow and stem cells to his father.

However, with this new diagnosis, his family and friends would certainly hope that Sager would keep his positivity and not lose hope.