The Spanish defender was forced to withdraw from Antonio Conte’s starting line-up at Old Trafford due to illness last weekend.
Chelsea went on to lose 2-0 to bitter rivals Manchester United as Tottenham moved to within four points of the Premier League leaders.
Alonso has been ever-present at left wing-back throughout the 2016-17 season following his transfer from Serie A side Fiorentina last summer.
The 26-year-old has made a big contribution from wing-back after a return of five goals and two assists in 27 appearances in the English top flight.
Former Arsenal defender Keown believes Chelsea will need Alonso to be fit if Conte’s side are to beat Tottenham in the FA Cup semi-final at Wembley.
“Chelsea will need Marcos Alonso back fit. Conte made a mistake against Manchester United by moving Cesar Azpilicueta up to left wing back and bringing in Kurt Zouma at centre back,” Keown told the Daily Mail.
“When a key player like Alonso is injured you want to minimise the changes. Conte would have been better served by not upsetting the back three and just bringing in Willian on the left.”
Chelsea have lost two of their last four Premier League games following defeats by Manchester United and Crystal Palace.
Tottenham were 2-0 winners against the leaders at White Hart Lane.
MORE: Man United latest news
MORE: Arsenal latest news
MORE: Chelsea latest news
MORE: Liverpool latest news