$re = '/<a (?!data-link=)[^>]*>((?!<\/a>).*?)<\/a>/im';
$str = '<p><a data-link=\\"keepLink\\" href=\\"[1|9999|16|191967|256]\\">Daily Racing Link</a></p>\\r\\n<br>\\n <strong>OFFER – Get up to a £400 deposit bonus when you sign up with <a href="https://gateway.tracker.com/track-989">Fanduel</a>.</strong>';
$subst = "$1";
$result = preg_replace($re, $subst, $str);
echo "The result of the substitution is ".$result;
Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for PHP, please visit: http://php.net/manual/en/ref.pcre.php