With the calendar turning to July recently and the season being right at about the halfway mark fantasy owners should know their teams’ strengths and weaknesses and be actively pursuing trades and transactions to improve their teams for the stretch runs. Sometimes those moves might not be what you want to do but what you need to do.

You don’t want to trade Julio Teheran, but you might need to do it. In 12 starts since April 23 Teheran has put up a 2.27 ERA, 1.07 WHIP,  and 69 strikeouts and only 10 walks in 79.1 innings. But through his last start, on June 28, Teheran’s thrown 95.1 innings and is on pace for 190 innings – plus whatever may come in the playoffs. The most innings Teheran’s thrown in any season is 163, in 2011. I know all innings aren’t created equal, but it’s mostly a pretty good measure to go on. Teheran’s only thrown over 100 pitches in four starts, but in most of his starts he’s thrown over 90 pitches. He also doesn’t have any stinkers out there where he’s thrown fewer than 82.

Teheran’s gotten better as the season has progressed, so emphasize that as you shop him to other owners. He posted a 2.60 ERA in May and a sparkly 1.95 ERA in June. He’s increased his strikeout rate over the last two months and decreased his walk rate, too. His FIP and xFIP back up his superb last two months, also. You need to start shopping him now so the other owner sees an opportunity to have him on his or her roster for at least a couple months, assuming Teheran makes his starts for July and August.

Another rookie who’s pitched better as the season’s progressed is Miami’s Jose Fernandez. Even though his season-long numbers are very good, the 20-year-old has been amazing since April 29. In his last 12 starts Fernandez has put up a 2.23 ERA and 1.00 WHIP in 72.2 innings. He’s walking more batters than Teheran, but he’s just allowed 48 hits in those innings. He’s striking out over a batter an inning, too, and limiting opponents to a .257 OBP in those 12 starts. Fernandez’s ERA has dropped from 4.50 in April to 3.18 in May and all the way down to 1.67 in 32.1 June innings. After giving up six homers in April and May, Fernandez hasn’t allowed one in six starts in June and July.

Fernandez has limited batters to a BABIP under .300 in each month, but suffered from some bad luck stranding runners in April. His left on base numbers have corrected a bit over the last two months to right around 75 percent (league average is about 72 percent), and he posted even better numbers. I don’t see any reason – other than workload concerns – why Fernandez should falter down the stretch. But Hernandez is only 20, and he’s on pace for 184 innings, which would be 50 more than what he threw last year. I’m more concerned about Fernandez’s workload than I am about Teheran’s. But with the Marlins’ season going nowhere fast one would have to think that Fernandez is shut down sometime before the end of the season.

Finally, Shelby Miller has arguably been the best rookie pitcher this year. Even though he’s struck out 20 and walked just five in his last four starts Miller’s been severely hurt by the long ball – four allowed in just 18.1 innings. His ERA has risen all the way from 1.91 to – gasp – 2.71. Miller’s on pace for about 186 innings, which is about 37 more than what he threw last year. When shopping Miller don’t let other owners be scared off by hist last few starts. Every pitcher goes through ups and downs throughout the season, and Miller’s first two-and-a-half months were so good he was due for some regression. In June Miller posted season-best monthly strikeout and walk percentages of 27.5 and 4.6, respectively. And his K/BB was 6, which was also his best for a month in 2013. While his FIP and xFIP were both 3.00, his ERA was 4.31, thanks to those homers. His BABIP and LOB% were both the worst of the season, but they should revert closer to normal for the rest of the season.

These guys have been so good I wouldn’t blame you for holding on to them the rest of the season. Two of the three are in the middle of a playoff race so their teams could keep running them out there. But even if they do a case of fatigue is certainly very possible, and that would be even worse than skipping a start or putting them on the DL just for a break. Successful fantasy owners know when to let go of their late-round draft pick or waiver-wire find. Cash in when the price is right, and don’t hold on and see their values fall.