New York Jets running back Braelon Allen was placed on injured reserve with a sprained MCL on Thursday, three days after he injured his knee in a 27-21 loss to the Miami Dolphins. Allen served as the primary kickoff returner and short-yardage back for the Jets, helping spare Breece Hall in those situations as part of the NFL’s third-ranked rushing offense (144.5 yards per game, 5.2 yards per carry). Allen, 21, was hurt on a kickoff return in the second quarter after losing his first career fumble in the first. The Cowboys allowed 123.3 rushing yards per game in the first month of the season. Allen, who lost the fumble at the 1 at Miami in Week 4, has 18 carries for 76 yards this season.