 Complete the following phrase:  On 17 December 2016, Walcott scored the opening goal of a 21 loss at Manchester City before being substituted with a calf injury. He returned on 28 January 2017, scoring a hat-trick against former club Southampton in the fourth round of the FA Cup at St. Marys Stadium. He scored his 100th goal for Arsenal on 20 February in the next round of the FA Cup in a 20 victory over Sutton United. On 5 April, Walcott captained Arsenal to a 30 win in their league match at The Emirates against London rivals West Ham United; he scored the second goal, which was his 19th and last of the season and took his total to 104. He was an unused substitute as Arsenal beat Chelsea 21 in the 