Sentence:  Ryne Duren and Roland Sheldon , a rookie righthander who posted a 15 - 1 record last year for the Yanks ' Auburn ( N.Y. ) farm club of the Class - D New York-Pennsylvania League , are the <WSD>probable</WSD> rival pitchers . 
Meaning of the word marked with <WSD> tags:  likely but not certain to be or become true or real