Oxlade - Chamberlain scored in Monday 's pre-season 3 - 1 win over Mexican club Guadalajara Chivas in California .
Oxlade - Chamberlain damaged his knee in a Champions League match against Barcelona in February .
Oxlade - Chamberlain , who damaged his knee in a Champions League match against Barcelona in February , scored in Monday 's pre-season 3 - 1 win over Mexican club Guadalajara Chivas in California .