MySQL order by (str to int)

SELECT `01` FROM perf WHERE year = '2013' order by CAST(`01` AS INT) LIMIT 3

Column 01 has numeric values as varchar. I need to order top 3 of '01' as integer. Why doesn't this query working?

Table like this;

+----------------------+
| name | 01 | 02 | year|
+----------------------+
|name1 | 90 |*** |2013 |
+----------------------+
|name2 | 93 | 55 |2013 |
+----------------------+
|name3 |*** | 78 |2013 |
+----------------------+

Query should order by 01 (dismiss *) and give names and values.