Barcelona came back from 2 goals down, emerging as triumphant winners following a thrilling 4-2 clash against a lively Real Sociedad side at Anoeta Stadium on Sunday night. The win extended their ongoing unbeaten streak to 29 games in all competitions this season.Most consecutive unbeaten games in Barça's history:- 39 games: 32W 7D (Lucho 2015-16)- 29 games (ongoing): 23W 6D (Valverde 2017-18)- 28 games: 23W 5D (Guardiola 2010-11)Valverde is going for the record. pic.twitter.com/1gJetVfny9— FC Barcelona (@BarcaUniversal) January 15, 2018FC Barcelona are currently the only remaining unbeaten team in Europe, as Manchester City's own stellar streak was extinguished by Liverpool at Anfield. Here we take a look at 5 reasons why Barcelona have been so extraordinarily good in La Liga and why they've managed to pull so far ahead of their rivals:#5 Valverde's tactical successErnesto Valverde has done a splendid job at Barcelona this seasonAfter being thrust into the managerial post at FC Barcelona in the summer of 2017, Ernesto Valverde has certainly justified his appointment and is well on his way towards repaying the faith placed in him by the board.For this season, Valverde has stuck with a balanced 4-4-2 system, compared to the 4-3-3 or 3-4-3 system utilized by Luis Enrique in previous seasons. Valverde's awareness of balance and solidity, whilst disallowing any weakness towards the opposing team has worked dividends for his side.Valverde's system deploys his fullbacks to engage in combination play with supporting players such as Andres Iniesta and Ivan Rakitic. This, in turn, enables them to trouble stretched opposition defences.Furthermore, Valverde's has managed to extract some quality performances from new signing Paulinho, who has been deployed as a link between the midfield and the attacking front two of Messi and Suarez. His physicality and aerial threat have been put to good use and the stats speak for themselves.Paulinho's best season ever in terms of stats:8 goals in 35 Brazilian league games for Corinthians in 2011. Paulinho this season:8 goals in 18 La Liga games for FC Barcelona.— Seleção Brasileira (@BrazilStat) January 14, 2018Perhaps most importantly, Valverde's system imparts a free roaming role to Lionel Messi, allowing him to seek out spaces to manipulate and inflict damage upon oppositions.