Flight Crew Instrument; Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 80; Flight Crew Total 9000; Flight Crew Type 5600
Situational Awareness; Workload; Confusion; Communication Breakdown
Deviation - Altitude Crossing Restriction Not Met; Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy
Air Traffic Control Issued New Clearance; Flight Crew Requested ATC Assistance / Clarification; Flight Crew Returned To Clearance
Procedure; Chart Or Publication
On the KARLB2 arrival into ONT; we received a clearance to cross COAZT at 16;000 feet. Read back clearance. Was queried by Controller if we would make the restriction. We had just started our descent to make the restriction in PROF. Shortly thereafter; we received a heading 90 degrees left of course; then another heading 90 left. We asked the Controller as to the nature of the headings; and Controller replied 'for traffic.' Then informed us that the restriction was for GOATZ; not COAZT. These points are very close together on the STAR; and sound very similar.
I was up securing the aircraft; using the restroom and making sure the jumpseater (mechanic) put away the bunk. As I returned to the cockpit I heard the FO answering a radio call. He answered cleared to cross COAZT (KARLB2 arrival) at 16;000. FO reiterated to me we're cleared to cross COAZT at 16;000. Just as we started our descent the Controller (next Controller; not the issuing Controller); asked if we were going to make our restriction. I assured him [we] would. As we approached GOATZ the Controller gave us a vector to help us lose altitude. I inquired about this as we were on a normal vertical profile to make our restriction. The Controller responded we were to cross GOATZ (not COAZT) at 16;000. At that point we realized the mistake made with the previous Controller.  In my opinion; the names of these 2 fixes are way too similar to be on the same arrival. The name of the 2 fixes sound identical. After a long flight; this mistake I feel is too easy to make especially when there is only one person monitoring the radio for physiological (restroom) or any other reason.
Air carrier flight crew reported confusion while on KARLB2 STAR due the similar sounding fixes; GOATZ and COAZT.