Born in Santiago, Pinilla started his career with Club Universidad de Chile, leaving for European football and Italian giants Inter Milan in 2003 after signing a five-year contract.

[3] However, he was immediately sold to fellow Serie A club AC ChievoVerona (which acquired 50% of the player's rights),[4] and finished the 2003–04 season on loan again, to La Liga side RC Celta de Vigo,[5] not managing to score in a total of 12 league appearances.

In July 2004, Sporting CP bought 50% of his playing rights[6] and Pinilla, having spent much of the season on a low note, finished it with five goals, notably a hat-trick in a 3–0 away win against S.C. Braga on 1 May 2005.

[13] However, his return suffered a major setback when it was revealed the player had a fractured scaphoid wrist bone, a hidden injury sustained while still in Chile;[14] this put him out of action for a six further weeks.

At the Tuscan club, his once promising career got back on track, as he scored 24 goals in 24 games – including a series of 12 consecutive matches netting, a competition record[22]– and finished the campaign as the second best scorer despite missing more than a third of the fixtures through different injuries.

[23] He scored five league goals in his first 12 appearances, being an important attacking unit in a side that also included Abel Hernández, Massimo Maccarone and Fabrizio Miccoli.

[28] Whilst at the service of Atalanta BC, on loan, Pinilla scored arguably one of the best goals of the season in Italy on 4 April 2015, after netting through a bicycle kick in a 1–2 home loss to Torino FC.

[32] Pinilla earned the first of his 45 caps for Chile on 30 March 2003 in a friendly against Peru, closing a 2–0 win through a header,[33] and later led his country's scoring in the 2006 FIFA World Cup qualifiers with three goals.

[34] However, on 27 February 2007, whilst on loan to Universidad de Chile, he was caught in a hotel with María José López, the model wife of national team captain Luis Antonio Jiménez.