My general theory in life, and especially in fantasy baseball, is that conventional wisdom is usually completely wrong. Hell, it wasn’t too long ago that baseball wisdom believed that batting average is what counts, walks were useless, and you should bunt with your No. 2 hitter when the leadoff guy hits a double (well Dusty Baker still believes that). The point is, just because a lot of people are doing it doesn’t mean it’s a good idea.The point of this post is to identify three players who are owned in at least 75% of leagues you should consider dropping, paired with three players who are owned in fewer than 25% of leagues you should consider adding. Per usual, we will be using Yahoo! and ESPN ownership percentages.Drop – Josh Johnson, SP, TOR (Yahoo 80% & ESPN 63%)First the obvious — in four starts this year he has a 6.86 ERA and a 1.88 WHIP. On top of that he is having arm troubles already and we know all about his prior injuries, which cost him pretty much all of 2007, 2008, and 2011. The guy just can’t stay healthy and recently, even when he is healthy he isn’t very good. There are the aforementioned horrible numbers in 2013 and he wasn’t all that good last year either. On the surface his 3.81 ERA and 1.29 WHIP look OK, but digging deeper you see that all his good numbers came when he pitched in that giant Yosemite-like stadium the Marlins call home. On the road he gave up nearly 5 runs per game and had a 1.44 WHIP. Rogers Centre is no Marlins Park.Add – Kyle Kendrick, SP, PHI (Yahoo 25% & ESPN 23%)It has gone fairly unnoticed, but Kendrick has had a nice season so far. He is 2-1 with a 2.41 ERA and a 1.10 WHIP; capped off by his last start where he threw a three-hit shutout against the Mets. He’s not this good, but he is good. It all started the second half of last year. Kendrick revamped his repertoire, scrapping his slider and throwing his cut fastball much less in favor of his sinker and changeup. To put it bluntly, it has worked. The second half of last year he was 9-4 with a 2.87 ERA and 1.06 WHIP. His ground ball and strikeout rates are up and his walk rate is down. That’s a recipe for success.Drop — Justin Masterson, SP, CLE (Yahoo 81% & ESPN 92%)For some reason everyone seems to always think that Masterson is a better pitcher than he is. His ownership rates seem to speak to that. But he is really no different than he has always been. His problem is well documented; he just can’t get lefties out. He is trying a new approach this year by throwing his slider more often in an attempt to get it in on lefties. He’s done alright so far, limiting lefties to .262 AVG and a .658 OPS. I just don’t think it will last. His control is at best average — he gives up nearly 4 BB per game — and he is prone to getting blown up (e.g., his start against Boston where he surrendered 11 H and 4 R in 5 IP and his last start against the Royals where he was pummeled for 7 R and 9 H in 6 1/3 IP).Add – Jeremy Guthrie, SP, KC (Yahoo 24% & ESPN 32%)Guthrie really likes being in Kansas City. Maybe it’s the BBQ? More likely it’s Kauffman Stadium, which ranks in the middle of the pack in terms of homers given up as opposed to Camden and Coors, Guthrie’s previous home parks, that rank at the top. Whatever it is, since joining KC he has gone 8-3 with a 3.14 ERA and a 1.16 WHIP in 19 starts. He doesn’t strike out a ton of guys, and he won’t “wow” you, but he is a good solid No. 4 starter. People forget that when he was with Baltimore he threw five straight years of over 175 IP (three over 200 IP). His record was terrible during those years, but hey, so were the Orioles back then. These Royals are not those Orioles, and it wouldn’t surprise me at all if Guthrie won 13-15 games with an ERA in the mid to high 3s.Drop – Nick Markakis, OF, BAL (Yahoo 78% & ESPN 100%)I’ve heard Markakis described in the past as boringly awesome. He put up consistent numbers of a .290 BA, nearly 100 R and 90-100 RBI with double digit steals and homers to boot. Nothing that will blow you away, but damn good numbers nonetheless. Since 2010 though he has consistently declined. He’s simply hitting the ball on the ground way more than he used to. This year his GB/FB rate is at a nearly 2-to-1 clip. Maybe it’s still the residual effects of the broken thumb last year or maybe it’s just decline. He is no longer boringly awesome, but just plain boring.Add – Michael Saunders, OF, SEA (Yahoo 16% & ESPN 9%)I think that players on bad teams are overlooked simply because they are on bad teams. Imagine if a young player on the Cardinals or Yankees had 19 HR and 21 SB in only 550 PA last year. That guy would be drafted in every league, but because Saunders plays in the great northwest we all forget about him. He is locked in as the Mariners everyday leadoff hitter and CF. He hit for a decent average in the minors, but his BB and K rates kind of jump all over the place so it’s tough to get a read on how good a contact hitter he might be. But, even if he hits .260 (he hit .247 last year) I’ll take that with a 20-20 season on top of it.