Chicago White Sox star Liam Hendriks -- arguably the best closer in the MLB -- has been diagnosed with cancer ... and is slated to begin treatment for the disease ASAP.
The right-handed pitcher revealed the news on his social media page Sunday -- saying docs recently discovered he had non-Hodgkin's Lymphoma. He went on to say he'll begin medical care to try to eradicate it all on Monday.
The 33-year-old, though, vowed to beat it ... saying he's going to use "the same determination I have used when facing other obstacles in my life.