1. Texas Rangers 102-62
Nobody did more during the season than the Rangers, who landed the crowning jewel of the non-waiver trade deadline (Matt Garza) and the waiver deadline (Alex Rios).
The Rangers would have loved to start the year with these two guys on the roster, as Rios has become a vital part of the team's offense, and Garza provides the team with a third stud in the starting rotation.
Rios has batted .312 with since coming to Texas with 30 runs generated (RBI and runs scored). He has been a solid replacement for Nelson Cruz, and could have been a key piece throughout the year.
Garza, on the other hand, has had another good year in 2013, posting an ERA of 3.70 while going 9-4 with the Chicago Cubs and Rangers. While he has struggled a bit against AL hitters compared to the batters he faced in the NL, Garza would have given the team a feared rotation alongside Yu Darvish and Derek Holland.
The Rangers can no longer reach the 100-win plateau after losing their 63rd game earlier this week. However, if the team had Garza and Rios all year they would have had the best record in the AL.
2. Oakland Athletics 95-67
The Athletics have had a solid roster throughout the year, which is why the team's only notable acquisitions were Kurt Suzuki and Alberto Callaspo this year.
While Callaspo's .269 batting average isn't stellar, he has still played a minor role with the team since coming to Arlington.
Suzuki was the big splash for the team, and he has batted .292 in limited action since being acquired.
While neither of these guys are stars, they still would have helped the team win a few more games and hit 95 wins.
3. Los Angeles Angels 77-85
A disappointing year for the Angels wouldn't have changed even if the team started the season with its current roster.
The team would have lost Scott Downs and would have had Grant Green instead of Alberto Callaspo if it started the year with its current roster.
Green has actually played better for the Angels than Callaspo did, but the loss of Downs' services would have hurt the team. Downs' 1.84 ERA in 43 appearances shows just how vital he was to the team's success, as he could shut opponents down out of the bullpen.
The Angels wouldn't have lived up to their lofty expectations even with their current roster, and losing Downs would have been enough to put the team 10 games under .500.
4. Seattle Mariners 72-90
Losing Jeremy Bonderman and adding Humberto Quintero wouldn't have changed much for the Mariners, but the big move for the team was trading Michael Morse to the Baltimore Orioles.
Morse has had a down year, but he was still a big part of the team's offense. His .223 batting average is unimpressive, but his 13 home runs in 76 games with the M's made him one of the team's best power hitters.
The Mariners were in for a rough year from the beginning, but if the team hadn't benefited from Morse's power it would have been even worse.
5. Houston Astros 47-115
The Astros barely even make the cut as a major league team, and losing Bud Norris for the entire season would have been devastating.
The team dealt its best pitcher to the Baltimore Orioles earlier this year, so in this hypothetical situation it would lose Norris, Jose Veras and Justin Maxwell.
These three guys were keys part to a struggling team, and without them the Astros would have been frighteningly bad. The team wouldn't have even managed to scrape together 50 wins without them.