England struggled against the well organised and physically imposing Tunisian defence in their first match of the tournament.
Dele Alli picked up the knock during the 2-1 win over Tunisia with him tweeting that he was working to get back to full fitness.
Kane's brace of goals had enabled England to edge past a gritty Tunisia in its opening match at the FIFA World Cup in Russia.
Monday evening's game in Volgograd, which was decided by captain Harry Kane's injury-time header, had a 69.2 percent audience share at its peak.
It was a remarkable World Cup debut for Kane, who bore the added pressure of the captain's armband and the weight of a nation on his 24-year-old shoulders.
Harry Kane scored 46 goals in all competitions for Tottenham last season but had never before scored in a major tournament finals for England.
Ruben Loftus-Cheek has just four caps to his name and is not alone in having no previous major tournament experience in Southgate's 23-man squad.
Walker has been deployed as a right-sided centre-back in a back-three by manager Gareth Southgate and is likely to retain the spot against Tunisia in their Group G opener.