A statement on the Arsenal website said the 24-year-old was struggling with a "minor hip/groin injury".
The statement added: "The Arsenal forward sustained the problem in training with the national team on Thursday and will fly back on Saturday to be assessed by the Club's medical staff."
It is anticipated the winger will be sidelined for between seven and 10 days.
Walcott had been expected to start Friday night's 8-0 thrashing of San Marino but instead is now on Arsenal's list of injury doubts for their Premier League encounter with Reading at the Emirates Stadium on March 30.
Arsenal team-mate Alex Oxlade-Chamberlain started in his place in Serravalle and got on the scoresheet in the rout.
After the game, Hodgson told BBC Radio Five Live: "Theo overstretched slightly crossing a ball and immediately felt a slight problem in the pelvic area.
"He went straight off the pitch and had a scan this morning and it showed a slight tear in the pelvic muscle.
"It kept him out tonight and will keep him out on Tuesday but hopefully won't keep him out for much longer.
"We did all we could to stop him aggravating it but these things happen sometimes in training."
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