What amazes me is how many people say that and actually take it seriously. It's certainly unusual for a team to have won three World Series in six seasons, yet have the other three years be completely ordinary and miss the playoffs all three times.
Injuries were the culprit for most of that failure. Last year, injuries to Hunter Pence helped do the Giants in (one of the injuries was suffered when Cubs prospect Corey Black broke Pence's forearm in the first spring-training game a year ago). If you don't think that matters much, consider that the Giants were 34-17 in games Pence started, 50-61 when he didn't. Obviously it's not all him, but his replacements were not good.
Pence is at full strength again and the Giants return a good offensive club that scored just one fewer run than the Pirates did in 2015. Denard Span is the only major change, taking over in left field.
The Giants also had injury issues in their rotation last year, with only two starters (Madison Bumgarner and Chris Heston) making at least 30 starts. They have attempted to address this by signing two free agent starters, Johnny Cueto and former Cub Jeff Samardzija. Cueto had a rough time after he was traded to the Royals, but came up big in the postseason. Shark had a horrific year for the White Sox in 2015. Supposedly he was tipping his pitches all year and has fixed that issue. If those two pitch in top form, the Giants will have an excellent rotation.
Their bullpen is solid, with closer Santiago Casilla backed up by an able setup staff led by Sergio Romo.
The Giants should compete all year with the Dodgers for the N.L. West title; whichever one doesn't make it will be in competition with the N.L. Central powerhouses for one of the wild-card spots.
The Cubs visit San Francisco May 20-21-22 and the Giants will be at Wrigley Field for a four-game series September 1-2-3-4.