According to North American Wrestling Rankings, which started keeping track of wrestlers’ records and ranking them as of Nov. 2006, when Sheamus lost by DQ to Randy Orton on the 6/1/15 episode of Raw it was his 300th televised match as a singles wrestler, making him only the 4th wrestler [behind Randy Orton, Dolph Ziggler, and Kofi Kingston] to have wrestled that many televised singles matches!
The next wrestlers closing in on this milestone [as of 6/2/15] are John Cena [291 matches] and Kane [290 matches].
[NOTE: these records count t.v. and ppv singles matches since Nov. 2006 ONLY].