If you look at my avatar, you can guess what I think. But I think there are statistics to back me up also.
I think he'll probably get a lot of saves. Remember, he didn't even take over the job until mid may so I would guess that he would have had around 40 saves last season and the cubs should be better this season (although some would disagree) so I think he gets around 40. Looking at this era though...as a closer he had 12 ER in 51 innings which comes out to around 2.1. His whip is harder to figure and I'm lazy but it varied a lot last season
may - 1.38
june - 0.84
july - 1.63
august - 1.74
september - 0.96
overall (whole season, including starts) - 1.43
Furthermore, if you look at it, his BABIP was .317, which means he was not really unlucky, but still unlucky to a degree which should help the WHIP and ERA a bit.
I would expect the era to regress a little to around 2.6ish cause not many closers can keep the era at 2 and his whip should definitely be less than his total for the season but I don't expect it to be spectacular. I'd say around 1.1-1.3, improving throughout the season.
Now, I wouldn't be ready to say he's the next rivera even though these numbers seem that way. Those are optimistic guesses from a cubs fan that may or may not be reasonable.
Leyland said, "We thought we were getting a hell of a player, but Neifi simply did not perform well."