Nel clutched the back of his rightleg while batting in Surrey's second innings, in which Mark Ramprakash narrowly failed to become the first player in the country to score 1, 000 runs.
Former Louisville running back Michael Bush broke his rightleg in two places during a football game in 2006 and had surgery the following day to repair his tibia.
The Cottagers, who will be without suspended right-back Chris Baird for the second leg, must be admired for the way they held firm to the end, Schwarzer thwarting an angled effort from substitute Mladen Petric on 88 minutes.