The former Tottenham striker is carrying a hamstring injury.
"With Jermain, we have to get it right," Nelsen said in reference to Defoe, whose original diagnosis was a "mild" hamstring pull.
"If we have to sacrifice next week (road game April 19 in Dallas) . . . it's a long season and he's probably got something more in the summer (World Cup with England). So we have to take care of him."
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