Oxlade-Chamberlain had been sidelined for five months with a knee injury, and Jenkinson says having him available will be a major benefit for the rest of the season.
"It has been tough for him," he told Arsenal.com. "Chambo is a very positive guy in general, he's great to be around and that's why we get on so well and why we're such good friends.
"But I could notice when he was out that it was tough for him at times. With the first little spell, maybe you can get through it, but it's a long injury that he had and when you've been out for three or four months it can be tough mentally."
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