Here's a look at the transactions this week that had the most significant fantasy impact.
Jered Weaver, RHP - placed on the 15-day DL (lower back)
Garrett Richards, RHP - recalled from Triple-A Salt Lake
Impact: The Angels rotation suffered a blow Tuesday when its ace was placed on the DL with a strained lower back. Weaver has continued to dominate hitters this season, going 6-1 with a 2.61 ERA and 0.93 WHIP through 11 starts. He's expected to miss no more than two or three starts, with newly-recalled Richards filling his rotation spot in the meantime. Richards was 0-2 with a 5.79 ERA in seven appearances (three starts) last season and is probably only worth a look in deep AL-only leagues at this point.
Jonathan Lucroy, C - placed on the 15-day DL (right hand)
Martin Maldonado, C - recalled from Triple-A Nashville
Impact: Lucroy was off to a hot start offensively before he broke his right hand while in his hotel room Sunday night. The Brewers' young catcher was hitting a robust .345 with five home runs and 30 RBI through 43 games before suffering the injury. He's expected to be out at least six weeks. Backup catcher George Kottaras is nursing a sore hamstring, so Maldonado should receive some starts while he recovers. Kottaras has some pop in his bat and could help fill out a fantasy roster when healthy, but Maldonado isn't likely to be worth owning in most leagues.
Daniel Hudson, RHP - activated from the 15-day DL
Konrad Schmidt, C - optioned to Triple-A Reno
Impact: Hudson pitched fairly well Sunday against the Brewers after missing more than a month with a right shoulder impingement. A 16-game winner in his first full season in 2011, Hudson struggled early on this year, going 1-1 with a 6.00 ERA through three starts before the injury. Although he didn't factor into the decision Sunday, he did manage to hold Milwaukee to two earned runs on six hits and a walk through five innings, while striking out three. He should be stretched out over his next few starts, and his track record in both the major and minor leagues makes him a solid fantasy option. At just 25, he should only get better as he gets more experience under his belt. Left-hander Patrick Corbin had been optioned to Triple-A Reno last week to make room in the rotation for Hudson's return. Schmidt went 0-for-4 while providing the D-Backs with some catching depth while starter Miguel Montero recovered from a groin injury.
Ted Lilly, LHP - placed on the 15-day DL (left shoulder)
Mike Antonini, LHP - recalled from, and then optioned to Triple-A Albuquerque
Nathan Eovaldi, RHP - recalled from Double-A Chattanooga
Impact: Lilly finds himself on the shelf for the second time this season, as he will now miss some time due to inflammation in his left shoulder. His first stint on the DL caused him to miss the first couple of weeks of the season with neck stiffness. He pitched well in between DL stints, going 5-1 with a 3.14 ERA in eight starts. As of yet, there is no timetable for his return, but he should resume throwing by the end of this week. Eovaldi will fill in for the injured Lilly and could have some value in NL-only leagues. He was 1-2 with a 3.63 ERA in ten appearances for the Dodgers last year and at a young age of 22, he should only improve over time. Antonini spent just one day with the big league club and did not appear in a game.
Matt Kemp, OF - activated from the 15-day DL
Jerry Sands, OF - optioned to Triple-A Albuquerque
Matt Kemp, OF - place on 15-day DL (hamstring)
Alex Castellanos, OF - recalled from Triple-A Albuquerque
Impact: Kemp was activated off the disabled list Tuesday after missing a couple of weeks with a strained left hamstring. Unfortunately for the Dodgers (and his fantasy owners), he aggravated the injury while scoring during Wednesday's game against Milwaukee and was sent back to the DL on Thursday. Kemp put together a monster season in 2011, hitting .324 with 39 home runs, 115 runs scored, 126 RBI and 40 stolen bases. He was hitting well before hitting the DL this year as well, batting .359 with 12 home runs and 28 RBI through 34 games. Tony Gwynn Jr. would be the most likely candidate to receive extra playing time as a result of Kemp's re-injury, though he's unlikely to hold much fantasy value in most leagues. Sands hit .200 (4-for-20) in eight games with the Dodgers, and the Dodgers opted for Castellanos for Kemp's second DL stint.
Travis Hafner, DH - placed on the 15-day DL (right knee)
Scott Barnes, LHP - recalled from Triple-A Columbus
Impact: Despite failing to reach the 400-at-bat mark in any season since 2007, the injury-prone Hafner has shown that he still has some life left in his bat. The 34-year-old slugger has hit at least .270 in each of the last three years while reaching double digits in home runs, despite injuries that have significantly limited his playing time. He was off to a decent enough start this season, hitting .242 with six home runs and 23 RBI through 39 games. He is now expected to be out four to six weeks after undergoing successful surgery on his right knee. The Tribe is expected to use several players in the DH role as he recovers. Barnes will give the Indians an extra left-handed arm out of the pen.
Mark Reynolds, 3B - activated from the 15-day DL
Stu Pomeranz, RHP - placed on the 15-day DL (left oblique)
Impact: The O's slugging third baseman was off to a sluggish start before he was shut down for a couple of weeks with a strained muscle in his ribcage. After hitting a combined 141 home runs over the last four seasons (an average of about 35 per year), Reynolds managed just two long balls and nine RBI in 27 games before his injury this year. While the power should return, he is one of the most strikeout-prone hitters in all of baseball, and his .210 batting average over the last two seasons leaves much to be desired. Nick Johnson figures to lose the most playing time as a result of this move, as he had been getting semi-regular playing time at DH. Pomeranz made three relief appearances for Baltimore before being shut down with a strained left oblique.
Carlos Quentin, OF - activated from the 15-day DL
Blake Tekotte, OF - optioned to Triple-A Tucson
Impact: The oft-injured Quentin was acquired from the White Sox during the offseason, but spent the first couple of months of the 2012 season recovering from arthroscopic knee surgery. He finally returned to action Monday and has managed to go 7-for-12 with three home runs and six RBI in his first three games off the DL. Not a bad way to make a good first impression with his new team, though he has yet to play a home game at spacious and pitcher-friendly Petco Park. His injuries have prevented him from ever playing in more than 131 games in a single season, and his .252 career batting average isn't of much help to fantasy teams. On the plus side, he has managed to hit a combined 107 home runs over the last four seasons, despite missing 170 games over that time. Expect a dropoff in his production this year due to the dimensions of his home ballpark, but Quentin should still put up some decent numbers as long as he's healthy. Tekotte was 2-for-15 in 11 games with the Padres and is likely to be called up again the next time San Diego needs another outfielder.
Roy Halladay, RHP - placed on the 15-day DL (right lat)
Erik Kratz, C - recalled from Triple-A Lehigh Valley
Impact: Halladay had amassed a total of 1,414.2 innings the last six years (an average of over 235 innings per season), making him one of baseball's most durable hurlers coming into this season. He'll now be sidelined for six to eight weeks with a strained right lat. That injury comes as a huge blow to the Phillies, who are trying to stay out of the basement in the highly competitive NL East. Dave Bush and Scott Elarton (both pitching at Triple-A) have been mentioned as possible replacements in the rotation, but neither pitcher is worth taking a chance on in most fantasy leagues. Kratz will serve as Philadelphia's third catcher and is not fantasy-relevant.
Hideki Matsui, OF-DH - contract purchased from Triple-A Durham
Stephen Vogt, OF - optioned to Triple-A Durham
Impact: Matsui finally returned to the major leagues on Tuesday, about a month after being inked to a minor league deal by the Rays. Godzilla posted the worst season of his major league career last year with Oakland, as he hit just .251 with 12 home runs and 72 RBI. With Desmond Jennings expected to return from the DL shortly and with a packed outfield and DH situation in T.B., it remains unclear as to how Matsui will be used. The most likely situation would involve Ben Zobrist moving to second base, with Will Rhymes and Elliot Johnson losing playing time as a result. Vogt was absolutely terrible offensively with Tampa Bay, as he went hitless in 17 at-bats.