The word marathoners is playable in Words With Friends™, no blanks required. Because it is longer than 7 letters, you would have to play off an existing word or do it in several moves.
Words With Friends™ Letter Score: 17
Highest Scoring Words With Friends™ Play In The Letters
Seven Letter Word Alert: (50 words)
aerator, anomers, another, anthems, anthers, armrest, artsman, artsmen, atoners, earshot, enamors, errants, hamster, hoarser, hornets, maestro, mantras, martens, matrons, menorah, mentors, meronts, moaners, monster, mortars, mothers, narrate, norther, oarsman, oarsmen, ornater, ranters, reharms, reroast, rhetors, roamers, roaster, senator, shorten, shorter, smarten, smarter, smother, snorter, thermos, thrones, tonearm, trasher, treason, tremors