If he can provide the same or similar impact against the Vikings and in our playoff game(s) that he has the past few games then he would show me enough (now against two very good lines) to fully believe that he could be a productive DE for this team in the upcoming years and I will no longer question him.
Then again I think the bigger reason he is having an impact is because Raji is playing so well right now. Raji and Matthews are having such huge impacts on the O-lines right now that our other pass rushers are able to come in and have a significant impacts that they would normally not be able to generate without Matthews and Raji. Don't get me wrong Neal is playing very well and has shown a lot of ability these past few weeks, as well as flashes throughout the season that he, on his own, is an effective pass-rusher. I just don't think what he has done recently is 100% warranted on him as much as it is on Raji playing much better and Matthews being healthy.
IMO if Raji and Matthews continue to play like this our pass rush will be good enough that our D will be very formidable come playoff time. Last time Raji played like this was the end of the 2010 season/ 2011 playoffs when our D was what won us Super Bowl XXXXV.