2012
The following season , however , he managed just 12 league appearances due to the emergence of Ben Roberts and the arrival of Mark Schwarzer .
 Ben Roberts, Mark Schwarzer
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: media, plant, vehicle, astronomical object, time, disease, animal, location, person, organization, mythical figure, food, biology, geographical phenomenon, instrument, event 
Text: {0} 
Answer:
 Ben Roberts, Mark Schwarzer