Do you guys remember two seasons ago when he was scoring at least a hat-trick and a super hat-trick in every Liga match (during the second part of the season) ? At this moment he was at the top of his career so far, with a lot of hunger and desire to show that he's the best in the world. He doesn't show the same hunger anymore but he's still the best in the world. It shows how good he is and how good he was.
Scoring a hattrick almost every game or so is an anomaly, no matter how good you are, even if you are Messi, it is simply not sustainable. So his failure to match that kind of record he had in the past does not and should not necessarily trigger the alarm bells to ring. If you think about it, it is either our opponents are getting better at defending against him and marking him, or he has declined, or both. I think two things are pretty clear, (1) he is quite cautious and reserved given that the WC is less than 3 months away and (2) Messi has still got it, the magic, the abilities to do it all over again. The only difference could be that he has slowed down a bit.
I personally think our opponents have become much better defending against Messi and our team, coupled with Messi being quite reserved and cautious, explains why we don't see those monstrous numbers he had before.