The Magpies midfielder is a booking away from missing the Swans' visit to St. James' Park.
Shelvey has accumulated nine yellow cards this season and will miss the upcoming visits of the Swans and Manchester City if he is booked against Southampton this weekend.
However, the England international will avoid a suspension if his tenth caution comes after the yellow card amnesty, which kicks in after Saturday's fixture.
Shelvey has been one of Newcastle's most prolific Premier League tacklers, averaging just over two a game so far, which is the fifth most of any Magpies player who has made five or more appearances this season.
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The 24-year-old left Swansea in favour of a move north in January, and earned his former side £12 million according to the BBC.
Shelvey made his Newcastle debut in a 2-1 win against West Ham United four days later - a result that lifted the Magpies above the Welsh club, temporarily, and out of the bottom three.
But the two sides have experienced contrasting runs of form since then, with Newcastle collecting four points from their last 27 available and the Swans picking up 18 from 33 to move 10 points clear of the drop.