It was United's decision to sign Dutch left-back Buttner that handed Shaw his big first-team break with the Saints.
A St Mary's source told the Sunday Mirror: "Southampton were going to sign Buttner, but he ended up going to Manchester United. They gave Danny Fox a go at left-back and then Luke was given a chance sooner than he probably expected.
"The club are determined not to sell Luke in January and Cortese values him very, very highly."
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