Belgium coach Marc Wilmots said the lack of game time his players are getting at club level cost them as they lost again.
After being unbeaten in 2013, Belgium – who easily qualified for the 2014 FIFA World Cup – finished the year with back-to-back losses.
The latest defeat came in a 3-2 loss to Japan in Brussels on Tuesday, days after being beaten by Colombia.
Wilmots said the next two months would be crucial to his team's chances of being successful in Brazil, but understands he has no control over how often his players get on the pitch.
"It was an excellent year in 2013, but we have ended up losing two games. It obviously does not please us to end the year in this fashion, but I think I know why," Wilmots said.
"We have not lost our playing qualities but sometimes when you do not play a lot for your club, there is a lack of pace and fitness.
"When you are not fully fit, you make mistakes and you do not defend as you would normally defend. I think this is the biggest project for us to do.
"The months of December and January will be very important for the national team, but I have very little influence on the amount of time the players play for their clubs."
Belgium took a 15th-minute lead through Kevin Mirallas, but Japan levelled thanks to Yoichiro Kakitani.
Goals from Keisuke Honda and Shinji Okazaki had Alberto Zaccheroni's men ahead before Toby Alderweireld scored what proved to be a 79th-minute consolation.
Wilmots said he experimented during the clash, one he felt Belgium 'dominated'.
"We tried a new formation tonight, a 4-2-3-1. That meant using Eden Hazard in support of Romelu Lukaku," he said.
"It went well for 20 minutes even if the Japanese were more threatening and had a few free players. However, I felt we had control of the game. We have not conceded opportunities.
"In the first half, the only one chance that Japan had was the one they scored. For the rest, we have dominated and played very well.
"In the second half, I rebalanced and made the substitution of Eden Hazard. This was expected because he has Champions League and (English) Premier League games (with Chelsea) coming up.
"This is a friendly game and I wanted to give playing time and chances to other players so they could try and impress."
|D. Van Buyten|
|Coach: M. Wilmots|
for E. Hazard 46'
for D. Mertens 62'
for M. Dembélé 72'
for R. Lukaku 76'
for D. Van Buyten 79'
|Scottish Premiership Preview: Dons seek to run Celtic closer|
|Paris Saint-Germain v Lyon: Ibrahimovic ready for season opener|
|Wolfsburg v Bayern Munich: De Bruyne centre of attention|
|Real Madrid 0 Milan 0 (10-9 on pens): Real lift second International Champions Cup|
|De Bruyne a doubt for Supercup clash|
|Reine-Adelaide needs time to blossom, says Walcott|
|Rodgers will not rush Ibe development|
|Napoli not interested in selling Higuain - De Laurentiis|
|Wilson agrees Bournemouth extension|
|Messi makes early Barcelona return|
|Ibrahimovic: My next move will be a very big surprise|
|Van Aanholt backs Lens to shine|
|Besiktas complete loan move for Gomez|
|McClaren: No decision on Coloccini future|
|Kane, Kaka hail goalkeeper Rimando|
|Chung eager to become FIFA president|
|Yedlin open to loan move|
|Tigres not scared of River trip - Ferretti|
|MLS Preview: Wright-Phillips, Lampard set to debut|
|´A draw is good for us´ - River´s Gallardo confident of Libertadores success|
|Di Maria poised for PSG switch - Blanc|
|Franjic: Bring on Bangladesh, Tajikistan|
|Van Gaal bemoans De Gea situation|
|MLS All-Stars 2 Tottenham 1: Kane stunner can´t spare Spurs|
|Manchester United 0 Paris Saint-Germain 2: Van Gaal´s defensive frailties exposed|
|Tigres UANL 0 River Plate 0: Visitors lose Gallardo in Copa Libertadores final first leg|
|Penedo parts ways with Galaxy|
|Benitez backs Mihajlovic, Milan to succeed|
|Barnetta joins Union in MLS|
|Allegri critical of Morata´s attitude|
|Franjic targets more A-League glory with City|
|Beto undaunted by Super Cup clash against Barca|
|Advocaat upbeat despite another Sunderland flop|
|McClaren praises Newcastle recruit Mitrovic|
|Payet will improve West Ham - Bilic|
|Pulis confirms interest in Lambert|
|Deila expects tough test in Baku|
|Drogba mobbed by Montreal Impact fans|
|UEFA Champions League Review: Ajax spurn two-goal lead at 10-man Rapid|
|Sunderland´s struggles continue as Doncaster cruise to win|
|Mahrez and Nugent on target in Leicester win|
|Mitrovic tastes debut defeat for Newcastle|
|Celtic 1 Qarabag 0: Boyata snatches crucial win|
|Jablonec 0 Copenhagen 1: Verbic cracker gives Danes the edge|
|Norwich sign Wisdom on loan from Liverpool|
|UEFA Europa League Preview: Koeman plays down importance of Vitesse links|
|Schneiderlin keen to learn from experienced duo|
|Mandzukic´s maiden Juventus goal seals win in Poland|
|Fofana completes Bastia loan|
|Deila delighted that Gordon pledges future to Celtic|
|Grenier ruled out for four months|
|Rooney: United squad ready for title challenge|
|Messi and Neymar available for start of season|
|Szczesny seals Roma switch|
|Benitez cools Mourinho war of words|
|Filipe Luis vows to win back Atletico fans|
|Besiktas in negotiations over Gomez switch|
|Kishna seals Lazio switch|
|Diaby completes Marseille move|
|Platini is bad for FIFA - Prince Ali|
|Bilic keen to make further additions|
|Brady makes Norwich move|
|Southampton complete Caulker loan|
|Rummenigge feels Muller ´will never leave´ Bayern|
|Platini to stand in FIFA presidential election|
|Howedes to remain Schalke skipper|
|Albion sign Hull defender Chester|
|Lucescu defends Fred selection amid doping allegations|
|Fabregas still in love with Arsenal|
|Luis Enrique ´happy´ with Barca´s US trip|
|Mourinho optimistic over Cahill and Costa|
|River owe Tigres´ Esqueda - Mercado|
|Van Gaal expecting big season from Shaw|
|Begovic keen to challenge Courtois|
|Mourinho launches attack on Benitez|
|CONMEBOL ´knocked on a lot of doors´ to keep half-spot - president|
|America 0 Benfica 0 (3-4 on penalties): Primeira Liga champions finally win|
|Napoli striker Higuain ´untouchable´ - Gabbiadini|
|Arsenal´s friendly form will boost confidence - Wenger|
|Nagatomo-Melo swap possible, says agent|
|Chelsea 2 Barcelona 2 (4-2 on penalties): Courtois stars for Premier League champions|
|Eriksen calls for ruthless Spurs|
|Pulis praises Berahino attitude|
|Alderweireld confident of top-four finish|
|Villa ready for tough Spurs clash|
|West Ham edge win on Carrow Road anniversary|
|Kozak scores twice as Villa draw at Wolves|
|Stanislas brace leads Bournemouth past Yeovil|
|Watford slip to friendly defeat at Cardiff|
|Lukaku injury sours Everton win at Dundee|
|UEFA Champions League Review: Fenerbahce draw blank as Monaco impress|
|West Brom earn friendly win over Walsall|
|Vardy at the double as Leicester beat Burton|
|Atletico impress in win over Oviedo|
|Herrera sacked by Mexico after ´punch´|
|Gerrard, Keane and Bradley pull out of MLS All-Star squad|
|Marseille reach Diaby agreement|
|Sammer thrilled with Vidal´s winning mentality|
|Platini expected to launch FIFA presidency bid|
|Romanov sacked me over Barca snub - Korobochka|
|Villa complete Crespo capture|
|Wolfsberger v Borussia Dortmund: Bender praises ´fun but exhausting´ training|
|Okaka swaps Sampdoria for Anderlecht|
|Southampton v Vitesse: Fonte excited for ´dream´ sojourn into Europe|
|Bournemouth agree King compensation|
|West Ham v Astra: Kouyate confident West Ham can progress|
|Vidal completes Bayern switch, signs four-year deal|
|Fabregas calls for Champions League improvement|
|BREAKING NEWS: Filipe Luis completes Atletico return|
|Bayern to present Vidal|
|Wenger unfazed by Mourinho´s spending jibe|
|Pellegrini: Sterling will justify price tag|
|Cavani hit with two-match Uruguay ban|
|Bonucci to remain at Juve until 2020|
|No bids for Berahino - West Brom|
|Putin: Blatter deserves a Nobel prize|
|Howe: Swansea a benchmark for Bournemouth|
|New Parma to play in Serie D|
|Mata vows to hit the goal trail at United|
|Drogba ´perfect fit´ for Montreal|
|Berahino ´not yet´ ready for Tottenham - Irvine|
|Romero lauds caring Van Gaal|
|Jese flying at Real under Rafa|
|Sampdoria unwilling to pay €10m for Balotelli|
|Mourinho talks up Arsenal title chances|
|Hull sign Ryan Taylor, Sam Clucas|
|Kane, Pochettino hail MLS All-Star test|
|Di Santo sorry for swift Werder departure|