La Liga 2015 16, Match Preview: Barcelona FC VS Athletic Bilbao
’s Inaki Williams lifts the trophy at the end of a second leg Spanish Super Cup soccer match between FC and at the stadium in Barcelona, Spain, Monday, Aug.17, 2015. After a 1-1 draw won the trophy following the first leg 4-0 win. (AP Photo/Manu Fernandez)

For a team that won it all in spectacular fashion last season, Barcelona begins the Spanish league plagued by doubts few could have imagined three months ago.

A shaky back line, an unexpected departure, and even a self-destructive outburst from the team’s best defender have given coach more than enough to muddle over before Sunday’s league opener at Athletic Bilbao.

La Liga 2015 16, Match Preview: Barcelona FC VS Athletic Bilbao
Athletic Bilbao’s Aritz Aduriz celebrates after scoring his side’s first goal during a second leg Spanish Super Cup soccer match between FC Barcelona and Athletic Bilbao at the Camp Nou stadium in Barcelona, Spain, Monday, Aug.17, 2015. (AP Photo/Manu Fernandez)

Barcelona would normally be favored in a trip to San Mames. But not after the Basques battered Barcelona 5-1 across the two legs of the Spanish Super Cup last weekend.

Where has the attacking verve and disciplined defense gone that swept the league, Champions League and Copa del Rey titles last spring?

Andres Iniesta, Barcelona’s new team captain following Hernandez’s departure after 17 seasons, has called for calm.

”We have only lost one title,” Iniesta said. ”Now it is time to pick ourselves up and focus on the league. Nobody is tired and there is no lack of heart.”

The European champions’ fitness had already been tested by Sevilla before the Bilbao debacle, when Barcelona squandered a 4-1 second-half lead before Pedro Rodriguez secured the UEFA Super Cup with a 5-4 victory in extra time.

That turned out to be Pedro’s last service for the club.

On Thursday, he decided to leave Barcelona after winning 20 titles and join Chelsea. Barcelona’s ace-in-the-hole forward had apparently had enough of watching and take his spot alongside Messi in Barcelona’s attack.

Luis Enrique acknowledged that Pedro’s future had been a distraction.

”It is a very difficult situation and it gets difficult to remain focused,” the coach said. ”And in that sense I am looking forward for the transfer period to be over once and for all.”

La Liga 2015 16, Match Preview: Barcelona FC VS Athletic Bilbao
FC Barcelona’s , from Argentina, left, and Neymar, from Brazil, attend a training session at the Sports Center FC Barcelona Joan Gamper in San Joan Despi, Spain, Saturday, Aug. 22, 2015. (AP Photo/Manu Fernandez)

Now Luis Enrique will have to find a replacement to complete his attack with Neymar also sidelined with the mumps.

There is also a hole in defense to fill for the Bilbao trip. Gerard Pique was suspended for the first four games of the season after he earned a rash red card for screaming at a line judge in Monday’s second leg against Bilbao.

Despite the team’s unsteady start to the campaign, the long view says Barcelona should again be fighting for titles come May.

The main reason, of course, is Messi. Add to that the productive partnership he quickly developed with Suarez and Neymar last season, which led to 122 goals between the three stars.

The 28-year-old Messi has picked right back up with three goals across the three official games played so far this season, and he should be as motivated as ever after a second straight disappointing summer with Argentina.

Messi responded to Argentina’s loss in the 2014 World Cup final with one of his best ever seasons with Barcelona, adding 58 goals to his all-time club record as well as improving his passing skills en route to collecting his 23rd, 24th and 25th career titles with the club.

Argentina came up short again this summer, falling to Chile in the Copa America final.

At stake is Messi’s bid to recover the title of world player of the year from ’ Cristiano Ronaldo and add to his unprecedented haul of four awards.

Barcelona will have a deeper squad come January, but likely some lingering problems as well.

New signings and Aleix Vidal will then join the squad following the club’s completion of the one-year transfer ban because it broke FIFA regulations regarding the transfers of underage players.

Despite being able to line up reinforcements for the second half of the season, Barcelona still faces several more off-pitch messes.

Court investigations continue forward into Messi’s alleged unpaid taxes and the club’s alleged attempts to hide the cost of the Neymar transfer in order to lower the taxes due.

La Liga 2015 16, Match Preview: Barcelona FC VS Athletic Bilbao
FC Barcelona’s Andres Iniesta looks on during a training session at the Sports Center FC Barcelona Joan Gamper in San Joan Despi, Spain, Saturday, Aug. 22, 2015. (AP Photo/Manu Fernandez)

So far, these legal issues have yet to harm the team’s performance, as seen last year when it cruised to the treble.

But their refusal to go away certainly won’t help the team that has set such a high standard for success for itself.